Oracle And Sunil Gahlot

Oracle Interview Q&A by Sunil Gahlot (OCA 9.i,OCP 9.i and MCP)

1. What are the components of physical database structure of Oracle database?
Oracle database is comprised of three types of files. One or more datafiles, two are more redo log files, and one or more control files.

2. What are the components of logical database structure of Oracle database?
There are tablespaces and database's schema objects.

3. What is a tablespace?
A database is divided into Logical Storage Unit called tablespaces. A tablespace is used to grouped related logical structures together.

4. What is SYSTEM tablespace and when is it created?
Every Oracle database contains a tablespace named SYSTEM, which is automatically created when the database is created. The SYSTEM tablespace always contains the data dictionary tables for the entire database.

5. Explain the relationship among database, tablespace and data file.
Each databases logically divided into one or more tablespaces one or more data files are explicitly created for each tablespace.

6. What is schema?
A schema is collection of database objects of a user.

7. What are Schema Objects?
Schema objects are the logical structures that directly refer to the database's data. Schema objects include tables, views, sequences, synonyms, indexes, clusters, database triggers, procedures, functions packages and database links.

8. Can objects of the same schema reside in different tablespaces?
Yes.

9. Can a tablespace hold objects from different schemes?
Yes.

10. What is Oracle table?
A table is the basic unit of data storage in an Oracle database. The tables of a database hold all of the user accessible data. Table data is stored in rows and columns.

11. What is an Oracle view?
A view is a virtual table. Every view has a query attached to it. (The query is a SELECT statement that identifies the columns and rows of the table(s) the view uses.)

11. What is Partial Backup ?
A Partial Backup is any operating system backup short of a full backup, taken while the database is open or shut down.

12. What is Mirrored on-line Redo Log ?
A mirrored on-line redo log consists of copies of on-line redo log files physically located on separate disks, changes made to one member of the group are made to all members.

13. What is Full Backup ?
A full backup is an operating system backup of all data files, on-line redo log files and control file that constitute ORACLE database and the parameter.

14. Can a View based on another View ?
Yes.

15. Can a Tablespace hold objects from different Schemes ?
Yes.

16. Can objects of the same Schema reside in different tablespaces.?
Yes.

17. What is the use of Control File ?
When an instance of an ORACLE database is started, its control file is used to identify the database and redo log files that must be opened for database operation to proceed. It is also used in database recovery.

18. Do View contain Data ?
Views do not contain or store data.

19. What are the Referential actions supported by FOREIGN KEY integrity constraint ?
UPDATE and DELETE Restrict - A referential integrity rule that disallows the update or deletion of referenced data. DELETE Cascade - When a referenced row is deleted all associated dependent rows are deleted.

20. What are the type of Synonyms?
There are two types of Synonyms Private and Public.

21. What is a Redo Log ?
The set of Redo Log files YSDATE,UID,USER or USERENV SQL functions, or the pseudo columns LEVEL or ROWNUM.

22. What is an Index Segment ?
Each Index has an Index segment that stores all of its data.

23. Explain the relationship among Database, Tablespace and Data file.?
Each databases logically divided into one or more tablespaces one or more data files are explicitly created for each tablespace

24. What are the different type of Segments ?
Data Segment, Index Segment, Rollback Segment and Temporary Segment.

25. What are Clusters ?
Clusters are groups of one or more tables physically stores together to share common columns and are often used together.

26. What is an Integrity Constrains ?
An integrity constraint is a declarative way to define a business rule for a column of a table.

27. What is an Index ?
An Index is an optional structure associated with a table to have direct access to rows, which can be created to increase the performance of data retrieval. Index can be created on one or more columns of a table.

28. What is an Extent ?
An Extent is a specific number of contiguous data blocks, obtained in a single allocation, and used to store a specific type of information.

29. What is a View ?
A view is a virtual table. Every view has a Query attached to it. (The Query is a SELECT statement that identifies the columns and rows of the table(s) the view uses.)

30. What is Table ?
A table is the basic unit of data storage in an ORACLE database. The tables of a database hold all of the user accessible data. Table data is stored in rows and columns.

31. Can a view based on another view?
Yes.

32. What are the advantages of views?
- Provide an additional level of table security, by restricting access to a predetermined set of rows and columns of a table.- Hide data complexity.- Simplify commands for the user.- Present the data in a different perspective from that of the base table.- Store complex queries.

33. What is an Oracle sequence?
A sequence generates a serial list of unique numbers for numerical columns of a database's tables.

34. What is a synonym?
A synonym is an alias for a table, view, sequence or program unit.

35. What are the types of synonyms?
There are two types of synonyms private and public.

36. What is a private synonym?
Only its owner can access a private synonym.

37. What is a public synonym?
Any database user can access a public synonym.

38. What are synonyms used for?
- Mask the real name and owner of an object.- Provide public access to an object- Provide location transparency for tables, views or program units of a remote database.- Simplify the SQL statements for database users.

39. What is an Oracle index?
An index is an optional structure associated with a table to have direct access to rows, which can be created to increase the performance of data retrieval. Index can be created on one or more columns of a table.

40. How are the index updates?
Indexes are automatically maintained and used by Oracle. Changes to table data are automatically incorporated into all relevant indexes.

41. What is a Tablespace?
A database is divided into Logical Storage Unit called tablespaces. A tablespace is used to grouped related logical structures together

42. What is Rollback Segment ?
A Database contains one or more Rollback Segments to temporarily store "undo" information.

43. What are the Characteristics of Data Files ?
A data file can be associated with only one database. Once created a data file can't change size. One or more data files form a logical unit of database storage called a tablespace.

44. How to define Data Block size ?
A data block size is specified for each ORACLE database when the database is created. A database users and allocated free database space in ORACLE datablocks. Block size is specified in INIT.ORA file and can’t be changed latter.

45. What does a Control file Contain ?
A Control file records the physical structure of the database. It contains the following information. Database NameNames and locations of a database's files and redolog files.Time stamp of database creation.

46.What is difference between UNIQUE constraint and PRIMARY KEY constraint ?
A column defined as UNIQUE can contain Nulls while a column defined as PRIMARY KEY can't contain Nulls.

47.What is Index Cluster ?
A Cluster with an index on the Cluster Key

48.When does a Transaction end ?
When it is committed or Rollbacked.

49. What is the effect of setting the value "ALL_ROWS" for OPTIMIZER_GOAL parameter of the ALTER SESSION command ? What are the factors that affect OPTIMIZER in choosing an Optimization approach ?
Answer The OPTIMIZER_MODE initialization parameter Statistics in the Data Dictionary the OPTIMIZER_GOAL parameter of the ALTER SESSION command hints in the statement.

50. What is the effect of setting the value "CHOOSE" for OPTIMIZER_GOAL, parameter of the ALTER SESSION Command ?
The Optimizer chooses Cost_based approach and optimizes with the goal of best throughput if statistics for atleast one of the tables accessed by the SQL statement exist in the data dictionary. Otherwise the OPTIMIZER chooses RULE_based approach.

51. What database block size should I use? (for DBA)
Oracle recommends that your database block size match, or be multiples of your operating system block size. One can use smaller block sizes, but the performance cost is significant. Your choice should depend on the type of application you are running. If you have many small transactions as with OLTP, use a smaller block size. With fewer but larger transactions, as with a DSS application, use a larger block size. If you are using a volume manager, consider your "operating system block size" to be 8K. This is because volume manager products use 8K blocks (and this is not configurable).

52. How does one create a new database? (for DBA)
One can create and modify Oracle databases using the Oracle "dbca" (Database Configuration Assistant) utility. The dbca utility is located in the $ORACLE_HOME/bin directory. The Oracle Universal Installer (oui) normally starts it after installing the database server software. One can also create databases manually using scripts. This option, however, is falling out of fashion, as it is quite involved and error prone. Look at this example for creating and Oracle 9i database: CONNECT SYS AS SYSDBAALTER SYSTEM SET DB_CREATE_FILE_DEST='/u01/oradata/';ALTER SYSTEM SET DB_CREATE_ONLINE_LOG_DEST_1='/u02/oradata/';ALTER SYSTEM SET DB_CREATE_ONLINE_LOG_DEST_2='/u03/oradata/';CREATE DATABASE;

53. What are the different approaches used by Optimizer in choosing an execution plan ?
Rule-based and Cost-based.

54. What does ROLLBACK do ?
ROLLBACK retracts any of the changes resulting from the SQL statements in the transaction.

How does one coalesce free space?(for DBA)
SMON coalesces free space (extents) into larger, contiguous extents every 2 hours and even then, only for a short period of time. SMON will not coalesce free space if a tablespace's default storage parameter "pctincrease" is set to 0. With Oracle 7.3 one can manually coalesce a tablespace using the ALTER TABLESPACE ... COALESCE; command, until then use:SQL> alter session set events 'immediate trace name coalesce level n';Where 'n' is the tablespace number you get from SELECT TS#, NAME FROM SYS.TS$; You can get status information about this process by selecting from the SYS.DBA_FREE_SPACE_COALESCED dictionary view.

55. How does one prevent tablespace fragmentation? (for DBA)
Always set PCTINCREASE to 0 or 100.Bizarre values for PCTINCREASE will contribute to fragmentation. For example if you set PCTINCREASE to 1 you will see that your extents are going to have weird and wacky sizes: 100K, 100K, 101K, 102K, etc. Such extents of bizarre size are rarely re-used in their entirety. PCTINCREASE of 0 or 100 gives you nice round extent sizes that can easily be reused. Eg. 100K, 100K, 200K, 400K, etc. Thiru Vadivelu contributed the following:Use the same extent size for all the segments in a given tablespace. Locally Managed tablespaces (available from 8i onwards) with uniform extent sizes virtually eliminates any tablespace fragmentation. Note that the number of extents per segment does not cause any performance issue anymore, unless they run into thousands and thousands where additional I/O may be required to fetch the additional blocks where extent maps of the segment are stored.

56. Where can one find the high water mark for a table? (for DBA)
There is no single system table, which contains the high water mark (HWM) for a table. A table's HWM can be calculated using the results from the following SQL statements: SELECT BLOCKSFROM DBA_SEGMENTSWHERE OWNER=UPPER(owner) AND SEGMENT_NAME = UPPER(table);ANALYZE TABLE owner.table ESTIMATE STATISTICS;SELECT EMPTY_BLOCKSFROM DBA_TABLESWHERE OWNER=UPPER(owner) AND SEGMENT_NAME = UPPER(table);Thus, the tables' HWM = (query result 1) - (query result 2) - 1 NOTE: You can also use the DBMS_SPACE package and calculate the HWM = TOTAL_BLOCKS - UNUSED_BLOCKS - 1.

57. What is COST-based approach to optimization?
Considering available access paths and determining the most efficient execution plan based on statistics in the data dictionary for the tables accessed by the statement and their associated clusters and indexes.

58. What does COMMIT do ?
COMMIT makes permanent the changes resulting from all SQL statements in the transaction. The changes made by the SQL statements of a transaction become visible to other user sessions transactions that start only after transaction is committed.

59. How are extents allocated to a segment? (for DBA)
Oracle8 and above rounds off extents to a multiple of 5 blocks when more than 5 blocks are requested. If one requests 16K or 2 blocks (assuming a 8K block size), Oracle doesn't round it up to 5 blocks, but it allocates 2 blocks or 16K as requested. If one asks for 8 blocks, Oracle will round it up to 10 blocks. Space allocation also depends upon the size of contiguous free space available. If one asks for 8 blocks and Oracle finds a contiguous free space that is exactly 8 blocks, it would give it you. If it were 9 blocks, Oracle would also give it to you. Clearly Oracle doesn't always round extents to a multiple of 5 blocks. The exception to this rule is locally managed tablespaces. If a tablespace is created with local extent management and the extent size is 64K, then Oracle allocates 64K or 8 blocks assuming 8K-block size. Oracle doesn't round it up to the multiple of 5 when a tablespace is locally managed.

60. Can one rename a database user (schema)? (for DBA)
No, this is listed as Enhancement Request 158508. Workaround: Do a user-level export of user Acreate new user BImport system/manager fromuser=A touser=BDrop user A

61. Define Transaction ?
A Transaction is a logical unit of work that comprises one or more SQL statements executed by a single user.

62. What is Read-Only Transaction ?
A Read-Only transaction ensures that the results of each query executed in the transaction are consistant with respect to the same point in time.

63. What is a deadlock ? Explain .
Two processes wating to update the rows of a table which are locked by the other process then deadlock arises. In a database environment this will often happen because of not issuing proper row lock commands. Poor design of front-end application may cause this situation and the performance of server will reduce drastically.These locks will be released automatically when a commit/rollback operation performed or any one of this processes being killed externally.

64. What is a Schema ?
The set of objects owned by user account is called the schema.

65. What is a cluster Key ?
The related columns of the tables are called the cluster key. The cluster key is indexed using a cluster index and its value is stored only once for multiple tables in the cluster.

66. What is Parallel Server ?
Multiple instances accessing the same database (Only In Multi-CPU environments)

67. What are the basic element of Base configuration of an oracle Database ?
It consists ofone or more data files.one or more control files.two or more redo log files.The Database containsmultiple users/schemasone or more rollback segmentsone or more tablespacesData dictionary tablesUser objects (table,indexes,views etc.,)The server that access the database consists ofSGA (Database buffer, Dictionary Cache Buffers, Redo log buffers, Shared SQL pool)SMON (System MONito)PMON (Process MONitor)LGWR (LoG Write)DBWR (Data Base Write)ARCH (ARCHiver)CKPT (Check Point)RECODispatcherUser Process with associated PGS

68. What is clusters ?
Group of tables physically stored together because they share common columns and are often used together is called Cluster.

69. What is an Index ? How it is implemented in Oracle Database ?
An index is a database structure used by the server to have direct access of a row in a table. An index is automatically created when a unique of primary key constraint clause is specified in create table comman (Ver 7.0)

70. What is a Database instance ? Explain
A database instance (Server) is a set of memory structure and background processes that access a set of database files.The process can be shared by all users. The memory structure that are used to store most queried data from database. This helps up to improve database performance by decreasing the amount of I/O performed against data file.

71. What is the use of ANALYZE command?
To perform one of these function on an index,table, or cluster:- To collect statistics about object used by the optimizer and store them in the data dictionary.- To delete statistics about the object used by object from the data dictionary.- To validate the structure of the object.- To identify migrated and chained rows of the table or cluster.

72. What is default tablespace?
The Tablespace to contain schema objects created without specifying a tablespace name.

73. What are the system resources that can be controlled through Profile ?
The number of concurrent sessions the user can establish the CPU processing time available to the user's session the CPU processing time available to a single call to ORACLE made by a SQL statement the amount of logical I/O available to the user's session the amout of logical I/O available to a single call to ORACLE made by a SQL statement the allowed amount of idle time for the user's session the allowed amount of connect time for the user's session.

74. What is Tablespace Quota ?
The collective amount of disk space available to the objects in a schema on a particular tablespace.

76. What are the different Levels of Auditing ?
Statement Auditing, Privilege Auditing and Object Auditing.

77. What is Statement Auditing ?
Statement auditing is the auditing of the powerful system privileges without regard to specifically named objects.

78. What are the database administrators utilities avaliable ?
SQL * DBA - This allows DBA to monitor and control an ORACLE database. SQL * Loader - It loads data from standard operating system files (Flat files) into ORACLE database tables. Export (EXP) and Import (imp) utilities allow you to move existing data in ORACLE format to and from ORACLE database.

79. How can you enable automatic archiving ?
Shut the databaseBackup the databaseModify/Include LOG_ARCHIVE_START_TRUE in init.ora file.Start up the database.

80. What are roles? How can we implement roles ?
Roles are the easiest way to grant and manage common privileges needed by different groups of database users. Creating roles and assigning provides to roles. Assign each role to group of users. This will simplify the job of assigning privileges to individual users.

81. What are Roles ?
Roles are named groups of related privileges that are granted to users or other roles.

82. What are the use of Roles ?
REDUCED GRANTING OF PRIVILEGES - Rather than explicitly granting the same set of privileges to many users a database administrator can grant the privileges for a group of related users granted to a role and then grant only the role to each member of the group. DYNAMIC PRIVILEGE MANAGEMENT - When the privileges of a group must change, only the privileges of the role need to be modified. The security domains of all users granted the group's role automatically reflect the changes made to the role.SELECTIVE AVAILABILITY OF PRIVILEGES - The roles granted to a user can be selectively enable (available for use) or disabled (not available for use). This allows specific control of a user's privileges in any given situation.APPLICATION AWARENESS - A database application can be designed to automatically enable and disable selective roles when a user attempts to use the application.

83. What is Privilege Auditing ?
Privilege auditing is the auditing of the use of powerful system privileges without regard to specifically named objects.

84. What is Object Auditing ?
Object auditing is the auditing of accesses to specific schema objects without regard to user.

85. What is Auditing ?
Monitoring of user access to aid in the investigation of database use.

85. How does one see the uptime for a database? (for DBA
Look at the following SQL query: SELECT to_char (startup_time,'DD-MON-YYYY HH24: MI: SS') "DB Startup Time"FROM sys.v_$instance;Marco Bergman provided the following alternative solution: SELECT to_char (logon_time,'Dy dd Mon HH24: MI: SS') "DB Startup Time"FROM sys.v_$sessionWHERE Sid=1 /* this is pmon *//Users still running on Oracle 7 can try one of the following queries: Column STARTED format a18 head 'STARTUP TIME'Select C.INSTANCE,to_date (JUL.VALUE, 'J') to_char (floor (SEC.VALUE/3600), '09') ':'-- Substr (to_char (mod (SEC.VALUE/60, 60), '09'), 2, 2) Substr (to_char (floor (mod (SEC.VALUE/60, 60)), '09'), 2, 2) '.' Substr (to_char (mod (SEC.VALUE, 60), '09'), 2, 2) STARTEDfrom SYS.V_$INSTANCE JUL,SYS.V_$INSTANCE SEC,SYS.V_$THREAD CWhere JUL.KEY like '%JULIAN%'and SEC.KEY like '%SECOND%';Select to_date (JUL.VALUE, 'J') to_char (to_date (SEC.VALUE, 'SSSSS'), ' HH24:MI:SS') STARTEDfrom SYS.V_$INSTANCE JUL,SYS.V_$INSTANCE SECwhere JUL.KEY like '%JULIAN%'and SEC.KEY like '%SECOND%';select to_char (to_date (JUL.VALUE, 'J') + (SEC.VALUE/86400), -Return a DATE'DD-MON-YY HH24:MI:SS') STARTEDfrom V$INSTANCE JUL,V$INSTANCE SECwhere JUL.KEY like '%JULIAN%'and SEC.KEY like '%SECOND%';

86. Where are my TEMPFILES, I don't see them in V$DATAFILE or DBA_DATA_FILE? (for DBA
Tempfiles, unlike normal datafiles, are not listed in v$datafile or dba_data_files. Instead query v$tempfile or dba_temp_files: SELECT * FROM v$tempfile;SELECT * FROM dba_temp_files;

87. How do I find used/free space in a TEMPORARY tablespace? (for DBA
Unlike normal tablespaces, true temporary tablespace information is not listed in DBA_FREE_SPACE. Instead use the V$TEMP_SPACE_HEADER view: SELECT tablespace_name, SUM (bytes used), SUM (bytes free)FROM V$temp_space_headerGROUP BY tablespace_name;

88. What is a profile ?
Each database user is assigned a Profile that specifies limitations on various system resources available to the user.

89. How will you enforce security using stored procedures?
Don't grant user access directly to tables within the application. Instead grant the ability to access the procedures that access the tables. When procedure executed it will execute the privilege of procedures owner. Users cannot access tables except via the procedure.

90. How can one see who is using a temporary segment? (for DBA
For every user using temporary space, there is an entry in SYS.V$_LOCK with type 'TS'. All temporary segments are named 'ffff.bbbb' where 'ffff' is the file it is in and 'bbbb' is first block of the segment. If your temporary tablespace is set to TEMPORARY, all sorts are done in one large temporary segment. For usage stats, see SYS.V_$SORT_SEGMENT From Oracle 8.0, one can just query SYS.v$sort_usage. Look at these examples: select s.username, u."USER", u.tablespace, u.contents, u.extents, u.blocksfrom sys.v_$session s, sys.v_$sort_usage uwhere s.addr = u.session_addr/select s.osuser, s.process, s.username, s.serial#, Sum (u.blocks)*vp.value/1024 sort_sizefrom sys.v_$session s, sys.v_$sort_usage u, sys.v_$parameter VPwhere s.saddr = u.session_addr and vp.name = 'db_block_size'and s.osuser like '&1' group by s.osuser, s.process, s.username, s.serial#, vp.value/

91. How does one get the view definition of fixed views/tables?
Query v$fixed_view_definition. Example: SELECT * FROM v$fixed_view_definition WHERE view_name='V$SESSION';

92. What are the dictionary tables used to monitor a database spaces ?
DBA_FREE_SPACEDBA_SEGMENTSDBA_DATA_FILES.

93. How can we specify the Archived log file name format and destination?
By setting the following values in init.ora file. LOG_ARCHIVE_FORMAT = arch %S/s/T/tarc (%S - Log sequence number and is zero left paded, %s - Log sequence number not padded. %T - Thread number lef-zero-paded and %t - Thread number not padded). The file name created is arch 0001 are if %S is used. LOG_ARCHIVE_DEST = path.

94. What is user Account in Oracle database?
An user account is not a physical structure in Database but it is having important relationship to the objects in the database and will be having certain privileges.

95. When will the data in the snapshot log be used?
We must be able to create a after row trigger on table (i.e., it should be not be already available) After giving table privileges. We cannot specify snapshot log name because oracle uses the name of the master table in the name of the database objects that support its snapshot log. The master table name should be less than or equal to 23 characters. (The table name created will be MLOGS_tablename, and trigger name will be TLOGS name).

96. What dynamic data replication?
Updating or Inserting records in remote database through database triggers. It may fail if remote database is having any problem.

97. What is Two-Phase Commit ?
Two-phase commit is mechanism that guarantees a distributed transaction either commits on all involved nodes or rolls back on all involved nodes to maintain data consistency across the global distributed database. It has two phase, a Prepare Phase and a Commit Phase.

98. How can you Enforce Referential Integrity in snapshots ?
Time the references to occur when master tables are not in use. Peform the reference the manually immdiately locking the master tables. We can join tables in snopshots by creating a complex snapshots that will based on the master tables.

99. What is a SQL * NET?
SQL *NET is ORACLE's mechanism for interfacing with the communication protocols used by the networks that facilitate distributed processing and distributed databases. It is used in Clint-Server and Server-Server communications.

100. What is a SNAPSHOT ?
Snapshots are read-only copies of a master table located on a remote node which is periodically refreshed to reflect changes made to the master table.

101. What is the mechanism provided by ORACLE for table replication ?
Snapshots and SNAPSHOT LOGs

102. What is snapshots?
Snapshot is an object used to dynamically replicate data between distribute database at specified time intervals. In ver 7.0 they are read only.

103. What are the various type of snapshots?
Simple and Complex.

104. Describe two phases of Two-phase commit ?
Prepare phase - The global coordinator (initiating node) ask a participants to prepare (to promise to commit or rollback the transaction, even if there is a failure) Commit - Phase - If all participants respond to the coordinator that they are prepared, the coordinator asks all nodes to commit the transaction, if all participants cannot prepare, the coordinator asks all nodes to roll back the transaction.

105. What is snapshot log ?
It is a table that maintains a record of modifications to the master table in a snapshot. It is stored in the same database as master table and is only available for simple snapshots. It should be created before creating snapshots.

106. What are the benefits of distributed options in databases?
Database on other servers can be updated and those transactions can be grouped together with others in a logical unit.Database uses a two-phase commit.

107. What are the options available to refresh snapshots ?
COMPLETE - Tables are completely regenerated using the snapshots query and the master tables every time the snapshot referenced.FAST - If simple snapshot used then a snapshot log can be used to send the changes to the snapshot tables.FORCE - Default value. If possible it performs a FAST refresh; Otherwise it will perform a complete refresh.

108. What is a SNAPSHOT LOG ?
A snapshot log is a table in the master database that is associated with the master table. ORACLE uses a snapshot log to track the rows that have been updated in the master table. Snapshot logs are used in updating the snapshots based on the master table.

109. What is Distributed database ?
A distributed database is a network of databases managed by multiple database servers that appears to a user as single logical database. The data of all databases in the distributed database can be simultaneously accessed and modified.

110. How can we reduce the network traffic?
- Replication of data in distributed environment.- Using snapshots to replicate data.- Using remote procedure calls.

111. Differentiate simple and complex, snapshots ?
- A simple snapshot is based on a query that does not contains GROUP BY clauses, CONNECT BY clauses, JOINs, sub-query or snashot of operations.- A complex snapshots contain atleast any one of the above.

112. What are the Built-ins used for sending Parameters to forms?
You can pass parameter values to a form when an application executes the call_form, New_form, Open_form or Run_product.

113. Can you have more than one content canvas view attached with a window?
Yes. Each window you create must have atleast one content canvas view assigned to it. You can also create a window that has manipulated content canvas view. At run time only one of the content canvas views assign to a window is displayed at a time.

114. Is the After report trigger fired if the report execution fails?
Yes.

115. Does a Before form trigger fire when the parameter form is suppressed?
Yes.

116. What is SGA?
The System Global Area in an Oracle database is the area in memory to facilitate the transfer of information between users. It holds the most recently requested structural information between users. It holds the most recently requested structural information about the database. The structure is database buffers, dictionary cache, redo log buffer and shared pool area.

117. What is a shared pool?
The data dictionary cache is stored in an area in SGA called the shared pool. This will allow sharing of parsed SQL statements among concurrent users.

118. What is mean by Program Global Area (PGA)?
It is area in memory that is used by a single Oracle user process.

119. What is a data segment?
Data segment are the physical areas within a database block in which the data associated with tables and clusters are stored.

120. What are the factors causing the reparsing of SQL statements in SGA?
Due to insufficient shared pool size.Monitor the ratio of the reloads takes place while executing SQL statements. If the ratio is greater than 1 then increase the SHARED_POOL_SIZE.
121. What are clusters?
Clusters are groups of one or more tables physically stores together to share common columns and are often used together.

122. What is cluster key?
The related columns of the tables in a cluster are called the cluster key.

123. Do a view contain data?
Views do not contain or store data.

124. What is user Account in Oracle database?
A user account is not a physical structure in database but it is having important relationship to the objects in the database and will be having certain privileges.

125. How will you enforce security using stored procedures?
Don't grant user access directly to tables within the application. Instead grant the ability to access the procedures that access the tables. When procedure executed it will execute the privilege of procedures owner. Users cannot access tables except via the procedure.

126. What are the dictionary tables used to monitor a database space?
DBA_FREE_SPACEDBA_SEGMENTSDBA_DATA_FILES.
167. How does one do off-line database backups? (for DBA
Shut down the database from sqlplus or server manager. Backup all files to secondary storage (eg. tapes). Ensure that you backup all data files, all control files and all log files. When completed, restart your database.Do the following queries to get a list of all files that needs to be backed up: select name from sys.v_$datafile;select member from sys.v_$logfile;select name from sys.v_$controlfile;Sometimes Oracle takes forever to shutdown with the "immediate" option. As workaround to this problem, shutdown using these commands: alter system checkpoint;shutdown abortstartup restrictshutdown immediateNote that if you database is in ARCHIVELOG mode, one can still use archived log files to roll forward from an off-line backup. If you cannot take your database down for a cold (off-line) backup at a convenient time, switch your database into ARCHIVELOG mode and perform hot (on-line) backups.

168. What is the difference between SHOW_EDITOR and EDIT_TEXTITEM?
Show editor is the generic built-in which accepts any editor name and takes some input string and returns modified output string. Whereas the edit_textitem built-in needs the input focus to be in the text item before the built-in is executed.

169. What are the built-ins that are used to Attach an LOV programmatically to an item?
set_item_propertyget_item_property(by setting the LOV_NAME property)

170. How does one do on-line database backups? (for DBA
Each tablespace that needs to be backed-up must be switched into backup mode before copying the files out to secondary storage (tapes). Look at this simple example. ALTER TABLESPACE xyz BEGIN BACKUP;! cp xyfFile1 /backupDir/ALTER TABLESPACE xyz END BACKUP;It is better to backup tablespace for tablespace than to put all tablespaces in backup mode. Backing them up separately incurs less overhead. When done, remember to backup your control files. Look at this example:ALTER SYSTEM SWITCH LOGFILE; -- Force log switch to update control file headers ALTER DATABASE BACKUP CONTROLFILE TO '/backupDir/control.dbf';NOTE: Do not run on-line backups during peak processing periods. Oracle will write complete database blocks instead of the normal deltas to redo log files while in backup mode. This will lead to excessive database archiving and even database freezes.

171. How does one backup a database using RMAN? (for DBA
The biggest advantage of RMAN is that it only backup used space in the database. Rman doesn't put tablespaces in backup mode, saving on redo generation overhead. RMAN will re-read database blocks until it gets a consistent image of it. Look at this simple backup example. rman target sys/*** nocatalog run { allocate channel t1 type disk;backup format '/app/oracle/db_backup/%d_t%t_s%s_p%p'( database ); release channel t1; }Example RMAN restore: rman target sys/*** nocatalog run {allocate channel t1 type disk;# set until time 'Aug 07 2000 :51';restore tablespace users; recover tablespace users; release channel t1; }
The examples above are extremely simplistic and only useful for illustrating basic concepts. By default Oracle uses the database controlfiles to store information about backups. Normally one would rather setup a RMAN catalog database to store RMAN metadata in. Read the Oracle Backup and Recovery Guide before implementing any RMAN backups. Note: RMAN cannot write image copies directly to tape. One needs to use a third-party media manager that integrates with RMAN to backup directly to tape. Alternatively one can backup to disk and then manually copy the backups to tape.

172. What are the different file extensions that are created by oracle reports?
Rep file and Rdf file.

173. What is strip sources generate options?
Removes the source code from the library file and generates a library files that contains only pcode. The resulting file can be used for final deployment, but can not be subsequently edited in the designer.ex. f45gen module=old_lib.pll userid=scott/tiger strip_source YES output_file

173. How does one put a database into ARCHIVELOG mode? (for DBA
The main reason for running in archivelog mode is that one can provide 24-hour availability and guarantee complete data recoverability. It is also necessary to enable ARCHIVELOG mode before one can start to use on-line database backups. To enable ARCHIVELOG mode, simply change your database startup command script, and bounce the database: SQLPLUS> connect sys as sysdbaSQLPLUS> startup mount exclusive;SQLPLUS> alter database archivelog;SQLPLUS> archive log start;SQLPLUS> alter database open;NOTE1: Remember to take a baseline database backup right after enabling archivelog mode. Without it one would not be able to recover. Also, implement an archivelog backup to prevent the archive log directory from filling-up. NOTE2: ARCHIVELOG mode was introduced with Oracle V6, and is essential for database point-in-time recovery. Archiving can be used in combination with on-line and off-line database backups. NOTE3: You may want to set the following INIT.ORA parameters when enabling ARCHIVELOG mode: log_archive_start=TRUE, log_archive_dest=... and log_archive_format=... NOTE4: You can change the archive log destination of a database on-line with the ARCHIVE LOG START TO 'directory'; statement. This statement is often used to switch archiving between a set of directories. NOTE5: When running Oracle Real Application Server (RAC), you need to shut down all nodes before changing the database to ARCHIVELOG mode.

174. What is the basic data structure that is required for creating an LOV?
Record Group.

175. How does one backup archived log files? (for DBA
One can backup archived log files using RMAN or any operating system backup utility. Remember to delete files after backing them up to prevent the archive log directory from filling up. If the archive log directory becomes full, your database will hang! Look at this simple RMAN backup script: RMAN> run {2> allocate channel dev1 type disk;3> backup4> format '/app/oracle/arch_backup/log_t%t_s%s_p%p'5> (archivelog all delete input);6> release channel dev1;7> }

176. Does Oracle write to data files in begin/hot backup mode? (for DBA
Oracle will stop updating file headers, but will continue to write data to the database files even if a tablespace is in backup mode. In backup mode, Oracle will write out complete changed blocks to the redo log files. Normally only deltas (changes) are logged to the redo logs. This is done to enable reconstruction of a block if only half of it was backed up (split blocks). Because of this, one should notice increased log activity and archiving during on-line backups.

470. What is Fine Grained Auditing? (for DBA
Fine Grained Auditing (DBMS_FGA) allows auditing records to be generated when certain rows are selected from a table. A list of defined policies can be obtained from DBA_AUDIT_POLICIES. Audit records are stored in DBA_FGA_AUDIT_TRAIL. Look at this example: o Add policy on table with autiting condition...execute dbms_fga.add_policy('HR', 'EMP', 'policy1', 'deptno > 10');o Must ANALYZE, this feature works with CBO (Cost Based Optimizer)analyze table EMP compute statistics;select * from EMP where c1 = 11; -- Will trigger auditingselect * from EMP where c1 = 09; -- No auditingo Now we can see the statments that triggered the auditing condition...select sqltext from sys.fga_log$;delete from sys.fga_log$;

471. What is a package ? What are the advantages of packages ? What is Pragma EXECPTION_INIT ? Explain the usage ?
The PRAGMA EXECPTION_INIT tells the complier to associate an exception with an oracle error. To get an error message of a specific oracle error. e.g. PRAGMA EXCEPTION_INIT (exception name, oracle error number)
472. What is Fine Grained Access Control? (for DBA
See question "What is a Virtual Private Database".

473. What is a Virtual Private Database? (for DBA
Oracle 8i introduced the notion of a Virtual Private Database (VPD). A VPD offers Fine-Grained Access Control (FGAC) for secure separation of data. This ensures that users only have access to data that pertains to them. Using this option, one could even store multiple companies' data within the same schema, without them knowing about it. VPD configuration is done via the DBMS_RLS (Row Level Security) package. Select from SYS.V$VPD_POLICY to see existing VPD configuration.

474. What is Raise_application_error ?
Raise_application_error is a procedure of package DBMS_STANDARD which allows to issue an user_defined error messages from stored sub-program or database trigger.

475. What is Oracle Label Security? (for DBA
Oracle Label Security (formerly called Trusted Oracle MLS RDBMS) uses the VPD (Virtual Private Database) feature of Oracle8i to implement row level security. Access to rows are restricted according to a user's security sensitivity tag or label. Oracle Label Security is configured, controlled and managed from the Policy Manager, an Enterprise Manager-based GUI utility.

476. Give the structure of the procedure ?
PROCEDURE name (parameter list.....)islocal variable declarationsBEGINExecutable statements.Exception.exception handlersend;

477. What is OEM (Oracle Enterprise Manager)? (for DBA
OEM is a set of systems management tools provided by Oracle Corporation for managing the Oracle environment. It provides tools to monitor the Oracle environment and automate tasks (both one-time and repetitive in nature) to take database administration a step closer to "Lights Out" management.

478. Question What is PL/SQL ?
PL/SQL is a procedural language that has both interactive SQL and procedural programming language constructs such as iteration, conditional branching.

479. What are the components of OEM? (for DBA
Oracle Enterprise Manager (OEM) has the following components: . Management Server (OMS): Middle tier server that handles communication with the intelligent agents. The OEM Console connects to the management server to monitor and configure the Oracle enterprise.. Console: This is a graphical interface from where one can schedule jobs, events, and monitor the database. The console can be opened from a Windows workstation, Unix XTerm (oemapp command) or Web browser session (oem_webstage). . Intelligent Agent (OIA): The OIA runs on the target database and takes care of the execution of jobs and events scheduled through the Console.

480. What happens if a procedure that updates a column of table X is called in a database trigger of the same table ?
Mutation of table occurs.

481. Is it possible to use Transaction control Statements such a ROLLBACK or COMMIT in Database Trigger ? Why ?
It is not possible. As triggers are defined for each table, if you use COMMIT of ROLLBACK in a trigger, it affects logical transaction processing.

482. How many types of database triggers can be specified on a table ? What are they ?
Insert Update DeleteBefore Row o.k. o.k. o.k.After Row o.k. o.k. o.k.Before Statement o.k. o.k. o.k.After Statement o.k. o.k. o.k.If FOR EACH ROW clause is specified, then the trigger for each Row affected by the statement.If WHEN clause is specified, the trigger fires according to the returned Boolean value.

483. What are the modes of parameters that can be passed to a procedure ?
IN,OUT,IN-OUT parameters.

484. Where the Pre_defined_exceptions are stored ?
In the standard package. Procedures, Functions & Packages ;

485. Write the order of precedence for validation of a column in a table ?I. done using Database triggers.ii. done using Integarity Constraints.?
I & ii.

486. Give the structure of the function ?
FUNCTION name (argument list .....) Return datatype islocal variable declarationsBeginexecutable statementsExceptionexecution handlersEnd;

487. Explain how procedures and functions are called in a PL/SQL block ?
Function is called as part of an expression.sal := calculate_sal ('a822');procedure is called as a PL/SQL statementcalculate_bonus ('A822');

488. What are advantages fo Stored Procedures?
Extensibility,Modularity, Reusability, Maintainability and one time compilation.

489. What is an Exception ? What are types of Exception ?
Exception is the error handling part of PL/SQL block. The types are Predefined and user defined. Some of Predefined exceptions are.CURSOR_ALREADY_OPENDUP_VAL_ON_INDEXNO_DATA_FOUNDTOO_MANY_ROWSINVALID_CURSORINVALID_NUMBERLOGON_DENIED NOT_LOGGED_ONPROGRAM-ERRORSTORAGE_ERRORTIMEOUT_ON_RESOURCEVALUE_ERRORZERO_DIVIDEOTHERS.

490. What are the PL/SQL Statements used in cursor processing ?
DECLARE CURSOR cursor name, OPEN cursor name, FETCH cursor name INTO or Record types, CLOSE cursor name.

491. What are the components of a PL/SQL Block ?
Declarative part, Executable part and Exception part.Datatypes PL/SQL

492. What is a database trigger ? Name some usages of database trigger ?
Database trigger is stored PL/SQL program unit associated with a specific database table. Usages are Audit data modifications, Log events transparently, Enforce complex business rules Derive column values automatically, Implement complex security authorizations. Maintain replicate tables.

493. What is a cursor ? Why Cursor is required ?
Cursor is a named private SQL area from where information can be accessed. Cursors are required to process rows individually for queries returning multiple rows.

494. What is a cursor for loop ?
Cursor for loop implicitly declares %ROWTYPE as loop index,opens a cursor, fetches rows of values from active set into fields in the record and closes when all the records have been processed.eg. FOR emp_rec IN C1 LOOPsalary_total := salary_total +emp_rec sal;END LOOP;

495. What will happen after commit statement ?
Cursor C1 isSelect empno,ename from emp;Beginopen C1; loopFetch C1 intoeno.ename;Exit WhenC1 %notfound;-----commit;end loop;end;The cursor having query as SELECT .... FOR UPDATE gets closed after COMMIT/ROLLBACK.The cursor having query as SELECT.... does not get closed even after COMMIT/ROLLBACK.

496. How packaged procedures and functions are called from the following?a. Stored procedure or anonymous blockb. an application program such a PRC *C, PRO* COBOLc. SQL *PLUS??
a. PACKAGE NAME.PROCEDURE NAME (parameters);variable := PACKAGE NAME.FUNCTION NAME (arguments);EXEC SQL EXECUTEb.BEGINPACKAGE NAME.PROCEDURE NAME (parameters)variable := PACKAGE NAME.FUNCTION NAME (arguments);END;END EXEC;c. EXECUTE PACKAGE NAME.PROCEDURE if the procedures does not have any out/in-out parameters. A function can not be called.

497. What is a stored procedure ?
A stored procedure is a sequence of statements that perform specific function.

498. What are the components of a PL/SQL block ?
A set of related declarations and procedural statements is called block.

499. What is difference between a PROCEDURE & FUNCTION ?
A FUNCTION is always returns a value using the return statement.A PROCEDURE may return one or more values through parameters or may not return at all.

500. What is difference between a Cursor declared in a procedure and Cursor declared in a package specification ?
A cursor declared in a package specification is global and can be accessed by other procedures or procedures in a package.A cursor declared in a procedure is local to the procedure that can not be accessed by other procedures.

501. What are the cursor attributes used in PL/SQL ?
%ISOPEN - to check whether cursor is open or not% ROWCOUNT - number of rows fetched/updated/deleted.% FOUND - to check whether cursor has fetched any row. True if rows are fetched.% NOT FOUND - to check whether cursor has fetched any row. True if no rows are featched.These attributes are proceeded with SQL for Implicit Cursors and with Cursor name for Explicit Cursors.

502. What are % TYPE and % ROWTYPE ? What are the advantages of using these over datatypes?
% TYPE provides the data type of a variable or a database column to that variable.% ROWTYPE provides the record type that represents a entire row of a table or view or columns selected in the cursor.The advantages are : I. Need not know about variable's data typeii. If the database definition of a column in a table changes, the data type of a variable changes accordingly.

503. What is difference between % ROWTYPE and TYPE RECORD ?
% ROWTYPE is to be used whenever query returns a entire row of a table or view.TYPE rec RECORD is to be used whenever query returns columns of different table or views and variables.E.g. TYPE r_emp is RECORD (eno emp.empno% type,ename emp ename %type );e_rec emp% ROWTYPEcursor c1 is select empno,deptno from emp;e_rec c1 %ROWTYPE.

504. What are the different types of PL/SQL program units that can be defined and stored in ORACLE database ?
Procedures and Functions,Packages and Database Triggers.
505. What are the advantages of having a Package ?
Increased functionality (for example,global package variables can be declared and used by any proecdure in the package) and performance (for example all objects of the package are parsed compiled, and loaded into memory once)

506. What are the uses of Database Trigger ?
Database triggers can be used to automatic data generation, audit data modifications, enforce complex Integrity constraints, and customize complex security authorizations.

507. What is a Procedure ?
A Procedure consist of a set of SQL and PL/SQL statements that are grouped together as a unit to solve a specific problem or perform a set of related tasks.

508. What is a Package ?
A Package is a collection of related procedures, functions, variables and other package constructs together as a unit in the database.

509. What is difference between Procedures and Functions ?
A Function returns a value to the caller where as a Procedure does not.

510. What is Database Trigger ?
A Database Trigger is procedure (set of SQL and PL/SQL statements) that is automatically executed as a result of an insert in,update to, or delete from a table.

511. Can the default values be assigned to actual parameters?
Yes

512. Can a primary key contain more than one columns?
Yes

513. What is an UTL_FILE.What are different procedures and functions associated with it?
UTL_FILE is a package that adds the ability to read and write to operating system files. Procedures associated with it are FCLOSE, FCLOSE_ALL and 5 procedures to output data to a file PUT, PUT_LINE, NEW_LINE, PUTF, FFLUSH.PUT, FFLUSH.PUT_LINE,FFLUSH.NEW_LINE. Functions associated with it are FOPEN, ISOPEN.

514. What are ORACLE PRECOMPILERS?
Using ORACLE PRECOMPILERS, SQL statements and PL/SQL blocks can be contained inside 3GL programs written in C,C++,COBOL,PASCAL, FORTRAN,PL/1 AND ADA. The Precompilers are known as Pro*C,Pro*Cobol,... This form of PL/SQL is known as embedded pl/sql,the language in which pl/sql is embedded is known as the host language. The prcompiler translates the embedded SQL and pl/sql ststements into calls to the precompiler runtime library.The output must be compiled and linked with this library to creater an executable.

515. What is difference between a formal and an actual parameter?
The variables declared in the procedure and which are passed, as arguments are called actual, the parameters in the procedure declaration. Actual parameters contain the values that are passed to a procedure and receive results. Formal parameters are the placeholders for the values of actual parameters

516. Differentiate between TRUNCATE and DELETE?
TRUNCATE deletes much faster than DELETETRUNCATEDELETEIt is a DDL statementIt is a DML statementIt is a one way trip,cannot ROLLBACKOne can RollbackDoesn't have selective features (where clause)HasDoesn't fire database triggersDoesIt requires disabling of referential constraints.

517. What should be the return type for a cursor variable.Can we use a scalar data type as return type?
The return type for a cursor must be a record type.It can be declared explicitly as a user-defined or %ROWTYPE can be used. eg TYPE t_studentsref IS REF CURSOR RETURN students%ROWTYPE

518. What are different Oracle database objects?
-TABLES –VIEWS –INDEXES –SYNONYMS –SEQUENCES -TABLESPACES etc

519. What is difference between SUBSTR and INSTR?
SUBSTR returns a specified portion of a string eg SUBSTR('BCDEF',4) output BCDE INSTR provides character position in which a pattern is found in a string. eg INSTR('ABC-DC-F','-',2) output 7 (2nd occurence of '-')

520. Display the number value in Words?
SQL> select sal, (to_char(to_date(sal,'j'), 'jsp')) from emp; the output like,SAL (TO_CHAR(TO_DATE(SAL,'J'),'JSP'))--------- ----------------------------------------800 eight hundred1600 one thousand six hundred1250 one thousand two hundred fiftyIf you want to add some text like, Rs. Three Thousand only.SQL> select sal "Salary ",(' Rs. ' (to_char(to_date(sal,'j'), 'Jsp')) ' only.'))"Sal in Words" from emp/Salary Sal in Words------- -----------------------------------------------800 Rs. Eight Hundred only.1600 Rs. One Thousand Six Hundred only.1250 Rs. One Thousand Two Hundred Fifty only.

521. What is difference between SQL and SQL*PLUS?
SQL*PLUS is a command line tool where as SQL and PL/SQL language interface and reporting tool. Its a command line tool that allows user to type SQL commands to be executed directly against an Oracle database. SQL is a language used to query the relational database(DML,DCL,DDL). SQL*PLUS commands are used to format query result, Set options, Edit SQL commands and PL/SQL.

522. What are various joins used while writing SUBQUERIES?
Self join-Its a join foreign key of a table references the same table. Outer Join--Its a join condition used where One can query all the rows of one of the tables in the join condition even though they don't satisfy the join condition.Equi-join--Its a join condition that retrieves rows from one or more tables in which one or more columns in one table are equal to one or more columns in the second table.

523. What a SELECT FOR UPDATE cursor represent.?
SELECT......FROM......FOR......UPDATE[OF column-reference][NOWAIT]The processing done in a fetch loop modifies the rows that have been retrieved by the cursor. A convenient way of modifying the rows is done by a method with two parts: the FOR UPDATE clause in the cursor declaration, WHERE CURRENT OF CLAUSE in an UPDATE or declaration statement.

524. What are various privileges that a user can grant to another user?
-SELECT-CONNECT-RESOURCES

525. Display the records between two range?
select rownum, empno, ename from emp where rowid in (select rowid from emp where rownum <=&upto minus select rowid from emp where rownum<&Start); 526. minvalue.sql Select the Nth lowest value from a table? select level, min('col_name') from my_table where level = '&n' connect by prior ('col_name') < 'col_name')group by level;Example:Given a table called emp with the following columns:-- id number-- name varchar2(20)-- sal number---- For the second lowest salary:-- select level, min(sal) from emp-- where level=2-- connect by prior sal < dept="123" course="101;UPDATE" current_credits="current_credits+v_numcreditsWHERE" dv="tb.dv);" sid_desc ="(GLOBAL_DBNAME" sid_name =" ...2." level =" '&n'"> 'col_name')group by level;Example:Given a table called emp with the following columns:-- id number-- name varchar2(20)-- sal number---- For the second highest salary:-- select level, max(sal) from emp-- where level=2-- connect by prior sal > sal-- group by level

590. Find out nth highest salary from emp table?
SELECT DISTINCT (a.sal) FROM EMP A WHERE &N = (SELECT COUNT (DISTINCT (b.sal)) FROM EMP B WHERE a.sal<=b.sal);For Eg:-Enter value for n: 2SAL---------3700 591. Suppose a customer table is having different columns like customer no, payments.What will be the query to select top three max payments? SELECT customer_no, payments from customer C1 WHERE 3<=(SELECT COUNT(*) from customer C2 WHERE C1.payment <= C2.payment) 592. How you will avoid your query from using indexes? SELECT * FROM emp Where emp_no+' '=12345;i.e you have to concatenate the column name with space within codes in the where condition.SELECT /*+ FULL(a) */ ename, emp_no from emp where emp_no=1234; i.e using HINTS 593. What utility is used to create a physical backup? Either rman or alter tablespace begin backup will do.. 594. What are the Back ground processes in Oracle and what are they. This is one of the most frequently asked question.There are basically 9 Processes but in a general system we need to mention the first five background processes.They do the house keeping activities for the Oracle and are common in any system.The various background processes in oracle are a) Data Base Writer(DBWR) :: Data Base Writer Writes Modified blocks from Database buffer cache to Data Files.This is required since the data is not written whenever a transaction is commited.b)LogWriter(LGWR) :: LogWriter writes the redo log entries to disk. Redo Log data is generated in redo log buffer of SGA. As transaction commits and log buffer fills, LGWR writes log entries into a online redo log file.c) System Monitor(SMON) :: The System Monitor performs instance recovery at instance startup.This is useful for recovery from system failured)Process Monitor(PMON) :: The Process Monitor peforms process recovery when user Process fails. Pmon Clears and Frees resources that process was using.e) CheckPoint(CKPT) :: At Specified times, all modified database buffers in SGA are written to data files by DBWR at Checkpoints and Updating all data files and control files of database to indicate the most recent checkpointf)Archieves(ARCH) :: The Archiver copies online redo log files to archival storal when they are busy.g) Recoveror(RECO) :: The Recoveror is used to resolve the distributed transaction in networkh) Dispatcher (Dnnn) :: The Dispatcher is useful in Multi Threaded Architecturei) Lckn :: We can have upto 10 lock processes for inter instance locking in parallel sql. 595. How many types of Sql Statements are there in Oracle There are basically 6 types of sql statments.They area) Data Defination Language(DDL) :: The DDL statments define and maintain objects and drop objects.b) Data Manipulation Language(DML) :: The DML statments manipulate database data.c) Transaction Control Statements :: Manage change by DMLd) Session Control :: Used to control the properties of current session enabling and disabling roles and changing .e.g :: Alter Statements,Set Rolee) System Control Statements :: Change Properties of Oracle Instance .e.g:: Alter Systemf) Embedded Sql :: Incorporate DDL,DML and T.C.S in Programming Language.e.g:: Using the Sql Statements in languages such as 'C', Open,Fetch, execute and close 596. What is a Transaction in Oracle A transaction is a Logical unit of work that compromises one or more SQL Statements executed by a single User. According to ANSI, a transaction begins with first executable statment and ends when it is explicitly commited or rolled back. 597. Key Words Used in Oracle The Key words that are used in Oracle are ::a) Commiting :: A transaction is said to be commited when the transaction makes permanent changes resulting from the SQL statements. b) Rollback :: A transaction that retracts any of the changes resulting from SQL statements in Transaction.c) SavePoint :: For long transactions that contain many SQL statements, intermediate markers or savepoints are declared. Savepoints can be used to divide a transactino into smaller points.d) Rolling Forward :: Process of applying redo log during recovery is called rolling forward.e) Cursor :: A cursor is a handle ( name or a pointer) for the memory associated with a specific stament. A cursor is basically an area allocated by Oracle for executing the Sql Statement. Oracle uses an implicit cursor statement for Single row query and Uses Explcit cursor for a multi row query.f) System Global Area(SGA) :: The SGA is a shared memory region allocated by the Oracle that contains Data and control information for one Oracle Instance.It consists of Database Buffer Cache and Redo log Buffer.g) Program Global Area (PGA) :: The PGA is a memory buffer that contains data and control information for server process.g) Database Buffer Cache :: Databese Buffer of SGA stores the most recently used blocks of datatbase data.The set of database buffers in an instance is called Database Buffer Cache.h) Redo log Buffer :: Redo log Buffer of SGA stores all the redo log entries. i) Redo Log Files :: Redo log files are set of files that protect altered database data in memory that has not been written to Data Files. They are basically used for backup when a database crashes.j) Process :: A Process is a 'thread of control' or mechansim in Operating System that executes series of steps. 598. What are Procedure,functions and Packages Procedures and functions consist of set of PL/SQL statements that are grouped together as a unit to solve a specific problem or perform set of related tasks.Procedures do not Return values while Functions return one One Value Packages :: Packages Provide a method of encapsulating and storing related procedures, functions, variables and other Package Contents 599. What are Database Triggers and Stored Procedures Database Triggers :: Database Triggers are Procedures that are automatically executed as a result of insert in, update to, or delete from table.Database triggers have the values old and new to denote the old value in the table before it is deleted and the new indicated the new value that will be used. DT are useful for implementing complex business rules which cannot be enforced using the integrity rules.We can have the trigger as Before trigger or After Trigger and at Statement or Row level. e.g:: operations insert,update ,delete 3 before ,after 3*2 A total of 6 combinatonsAt statment level(once for the trigger) or row level( for every execution ) 6 * 2 A total of 12. Thus a total of 12 combinations are there and the restriction of usage of 12 triggers has been lifted from Oracle 7.3 Onwards.Stored Procedures :: Stored Procedures are Procedures that are stored in Compiled form in the database.The advantage of using the stored procedures is that many users can use the same procedure in compiled and ready to use format. 600. How many Integrity Rules are there and what are they There are Three Integrity Rules. They are as follows ::a) Entity Integrity Rule :: The Entity Integrity Rule enforces that the Primary key cannot be Nullb) Foreign Key Integrity Rule :: The FKIR denotes that the relationship between the foreign key and the primary key has to be enforced.When there is data in Child Tables the Master tables cannot be deleted.c) Business Integrity Rules :: The Third Intigrity rule is about the complex business processes which cannot be implemented by the above 2 rules. 601. What are the Various Master and Detail Relation ships. The various Master and Detail Relationship area) NonIsolated :: The Master cannot be deleted when a child is exisitingb) Isolated :: The Master can be deleted when the child is exisitingc) Cascading :: The child gets deleted when the Master is deleted. 602. What are the Various Block Coordination Properties The various Block Coordination Properties are a) Immediate Default Setting. The Detail records are shown when the Master Record are shown.b) Deffered with Auto Query Oracle Forms defer fetching the detail records until the operator navigates to the detail block.c) Deffered with No Auto Query The operator must navigate to the detail block and explicitly execute a query 603. What is in all those X$ tables? (for DBA The following list attempts to describe some x$ tables. The list may not be complete or accurate, but represents an attempt to figure out what information they contain. One should generally not write queries against these tables as they are internal to Oracle, and Oracle may change them without any prior notification. X$K2GTE2 Kernel 2 Phase Commit Global Transaction Entry Fixed Table X$K2GTE Kernel 2 Phase Commit Global Transaction Entry Fixed Table X$BH Buffer headers contain information describing the current contents of a piece of the buffer cache X$KCBCBH Cache Buffer Current Buffer Header Fixed Table. It can predict the potential loss of decreasing the number of database buffers. The db_block_lru_statistics parameter has to be set to true to gather information in this table. X$KCVFH File Header Fixed Table X$KDNCE SGA Cache Entry Fixed Table X$KDNST Sequence Cache Statistics Fixed Table X$KDXHS Histogram structure Fixed Table X$KDXST Statistics collection Fixed Table X$KGHLU One-row summary of LRU statistics for the shared pool X$KGLBODY Derived from X$KGLOB (col kglhdnsp = 2) X$KGLCLUSTER Derived from X$KGLOB (col kglhdnsp = 5) X$KGLINDEX Derived from X$KGLOB (col kglhdnsp = 4) X$KGLLC Latch Clean-up state for library cache objects Fixed Table X$KGLPN Library cache pin Fixed Table X$KGLTABLE Derived from X$KGLOB (col kglhdnsp = 1) X$KGLTR Library Cache Translation Table entry Fixed Table X$KGLTRIGGER Derived from X$KGLOB (col kglhdnsp = 3) X$KGLXS Library Cache Access Table X$KKMMD Fixed table to look at what databases are mounted and their status X$KKSBV Cursor Cache Bind Variables X$KSMSP Each row represents a piece of memory in the shared pool X$KSQDN Global database name X$KSQST Enqueue statistics by type X$KSUCF Cost function for each Kernel Profile (join to X$KSUPL) X$KSUPL Resource Limit for each Kernel Profile X$KSURU Resource Usage for each Kernel Profile (join with X$KSUPL) X$KSQST Gets and waits for different types of enqueues X$KTTVS Indicate tablespace that has valid save undo segments X$KVII Internal instance parameters set at instance initialization X$KVIS Oracle Data Block (size_t type) variables X$KVIT Instance internal flags, variables and parameters that can change during the life of an instance X$KXFPCDS Client Dequeue Statistics X$KXFPCMS Client Messages Statistics X$KZDOS Represent an os role as defined by the operating system X$KZSRO Security state Role: List of enabled roles X$LE Lock Element: each PCM lock that is used by the buffer cache (gc_db_locks) X$MESSAGES Displays all the different messages that can be sent to the Background processes X$NLS_PARAMETERS NLS database parameters Handy X$table queriesSome handy queries based on the X$ memory tables: . Largest # blocks you can write at any given time: select kviival write_batch_sizefrom x$kvii where kviitag = 'kcbswc';. See the gets and waits for different types of enqueues: select * from x$ksqstwhere ksqstget > 0;Oracle Kernel SubsystemsListed below are some of the important subsystems in the Oracle kernel. This table might help you to read those dreaded trace files and internal messages. For example, if you see messages like this, you will at least know where they come from: OPIRIP: Uncaught error 447. Error stack:KCF: write/open error block=0x3e800 online=1

OPI
Oracle Program Interface
KK
Compilation Layer - Parse SQL, compile PL/SQL
KX
Execution Layer - Bind and execute SQL and PL/SQL
K2
Distributed Execution Layer - 2PC handling
NPI
Network Program Interface
KZ
Security Layer - Validate privs
KQ
Query Layer
RPI
Recursive Program Interface
KA
Access Layer
KD
Data Layer
KT
Transaction Layer
KC
Cache Layer
KS
Services Layer
KJ
Lock Manager Layer
KG
Generic Layer
KV
Kernel Variables (eg. x$KVIS and X$KVII)
S or ODS
Operating System Dependencies

604. What are the Different Optimisation Techniques
The Various Optimisation techniques are a) Execute Plan :: we can see the plan of the query and change it accordingly based on the indexesb) Optimizer_hint ::set_item_property('DeptBlock',OPTIMIZER_HINT,'FIRST_ROWS');Select /*+ First_Rows */ Deptno,Dname,Loc,Rowid from deptwhere (Deptno > 25)c) Optimize_Sql ::By setting the Optimize_Sql = No, Oracle Forms assigns a single cursor for all SQL statements.This slow downs the processing because for evertime the SQL must be parsed whenver they are executed.f45run module = my_firstform userid = scott/tiger optimize_sql = Nod) Optimize_Tp ::By setting the Optimize_Tp= No, Oracle Forms assigns seperate cursor only for each query SELECT statement. All other SQL statements reuse the cursor.f45run module = my_firstform userid = scott/tiger optimize_Tp = No

605. How does one change an Oracle user's password?(for DBA
Issue the following SQL command:ALTER USER IDENTIFIED BY ;From Oracle8 you can just type "password" from SQL*Plus, or if you need to change another user's password, type "password user_name". Look at this example: SQL> passwordChanging password for SCOTTOld password:New password:Retype new password:

606. How does one create and drop database users?
Look at these examples: CREATE USER scott IDENTIFIED BY tiger -- Assign passwordDEFAULT TABLESACE tools -- Assign space for table and index segmentsTEMPORARY TABLESPACE temp; -- Assign sort spaceDROP USER scott CASCADE; -- Remove userAfter creating a new user, assign the required privileges: GRANT CONNECT, RESOURCE TO scott;GRANT DBA TO scott; -- Make user a DB AdministratorRemember to give the user some space quota on its tablespaces: ALTER USER scott QUOTA UNLIMITED ON tools;

607. Who created all these users in my database?/ Can I drop this user? (for DBA
Oracle creates a number of default database users or schemas when a new database is created. Below are a few of them: SYS/CHANGE_ON_INSTALL or INTERNALOracle Data Dictionary/ CatalogCreated by: ?/rdbms/admin/sql.bsq and various cat*.sql scriptsCan password be changed: Yes (Do so right after the database was created)Can user be dropped: NOSYSTEM/MANAGERThe default DBA user name (please do not use SYS)Created by: ?/rdbms/admin/sql.bsqCan password be changed: Yes (Do so right after the database was created)Can user be dropped: NOOUTLN/OUTLNStored outlines for optimizer plan stabilityCreated by: ?/rdbms/admin/sql.bsqCan password be changed: Yes (Do so right after the database was created)Can user be dropped: NOSCOTT/TIGER, ADAMS/WOOD, JONES/STEEL, CLARK/CLOTH and BLAKE/PAPER.Training/ demonstration users containing the popular EMP and DEPT tablesCreated by: ?/rdbms/admin/utlsampl.sqlCan password be changed: YesCan user be dropped: YES - Drop users cascade from all production environmentsHR/HR (Human Resources), OE/OE (Order Entry), SH/SH (Sales History).Training/ demonstration users containing the popular EMPLOYEES and DEPARTMENTS tablesCreated by: ?/demo/schema/mksample.sqlCan password be changed: YesCan user be dropped: YES - Drop users cascade from all production environmentsCTXSYS/CTXSYSOracle interMedia (ConText Cartridge) administrator userCreated by: ?/ctx/admin/dr0csys.sqlTRACESVR/TRACEOracle Trace serverCreated by: ?/rdbms/admin/otrcsvr.sqlDBSNMP/DBSNMPOracle Intelligent agentCreated by: ?/rdbms/admin/catsnmp.sql, called from catalog.sqlCan password be changed: Yes - put the new password in snmp_rw.ora fileCan user be dropped: YES - Only if you do not use the Intelligent AgentsORDPLUGINS/ORDPLUGINSObject Relational Data (ORD) User used by Time Series, etc.Created by: ?/ord/admin/ordinst.sqlORDSYS/ORDSYSObject Relational Data (ORD) User used by Time Series, etcCreated by: ?/ord/admin/ordinst.sqlDSSYS/DSSYSOracle Dynamic Services and Syndication ServerCreated by: ?/ds/sql/dssys_init.sqlMDSYS/MDSYSOracle Spatial administrator userCreated by: ?/ord/admin/ordinst.sqlAURORA$ORB$UNAUTHENTICATED/INVALIDUsed for users who do not authenticate in Aurora/ORBCreated by: ?/javavm/install/init_orb.sql called from ?/javavm/install/initjvm.sqlPERFSTAT/PERFSTATOracle Statistics Package (STATSPACK) that supersedes UTLBSTAT/UTLESTATCreated by: ?/rdbms/admin/statscre.sqlRemember to change the passwords for the SYS and SYSTEM users immediately after installation! Except for the user SYS, there should be no problem altering these users to use a different default and temporary tablespace.

608. How does one enforce strict password control? (for DBA
By default Oracle's security is not extremely good. For example, Oracle will allow users to choose single character passwords and passwords that match their names and userids. Also, passwords don't ever expire. This means that one can hack an account for years without ever locking the user. From Oracle8 one can manage passwords through profiles. Some of the things that one can restrict: . FAILED_LOGIN_ATTEMPTS - failed login attempts before the account is locked . PASSWORD_LIFE_TIME - limits the number of days the same password can be used for authentication . PASSWORD_REUSE_TIME - number of days before a password can be reused . PASSWORD_REUSE_MAX - number of password changes required before the current password can be reused . PASSWORD_LOCK_TIME - number of days an account will be locked after maximum failed login attempts . PASSWORD_GRACE_TIME - number of days after the grace period begins during which a warning is issued and login is allowed . PASSWORD_VERIFY_FUNCTION - password complexity verification script Look at this simple example: CREATE PROFILE my_profile LIMITPASSWORD_LIFE_TIME 30;ALTER USER scott PROFILE my_profile;

609. How does one switch to another user in Oracle? (for DBA
Users normally use the "connect" statement to connect from one database user to another. However, DBAs can switch from one user to another without a password. Of course it is not advisable to bridge Oracle's security, but look at this example: SQL> select password from dba_users where username='SCOTT';PASSWORDF894844C34402B67SQL> alter user scott identified by lion;User altered.SQL> connect scott/lionConnected.REM Do whatever you like...SQL> connect system/managerConnected.SQL> alter user scott identified by values 'F894844C34402B67';User altered.SQL> connect scott/tigerConnected.

610. What are snap shots and views
Snapshots are mirror or replicas of tables. Views are built using the columns from one or more tables. The Single Table View can be updated but the view with multi table cannot be updated

611. What are the OOPS concepts in Oracle.
Oracle does implement the OOPS concepts. The best example is the Property Classes. We can categorise the properties by setting the visual attributes and then attach the property classes for the objects. OOPS supports the concepts of objects and classes and we can consider the peroperty classes as classes and the items as objects

612. What is the difference between candidate key, unique key and primary key
Candidate keys are the columns in the table that could be the primary keys and the primary key is the key that has been selected to identify the rows. Unique key is also useful for identifying the distinct rows in the table.)

613. What is concurrency
Cuncurrency is allowing simultaneous access of same data by different users. Locks useful for accesing the database area) Exclusive The exclusive lock is useful for locking the row when an insert,update or delete is being done.This lock should not be applied when we do only select from the row.b) Share lockWe can do the table as Share_Lock as many share_locks can be put on the same resource.

614. Previleges and Grants
Previleges are the right to execute a particulare type of SQL statements. e.g :: Right to Connect, Right to create, Right to resource Grants are given to the objects so that the object might be accessed accordingly.The grant has to be given by the owner of the object.

615. Table Space,Data Files,Parameter File, Control Files
Table Space :: The table space is useful for storing the data in the database.When a database is created two table spaces are created.a) System Table space :: This data file stores all the tables related to the system and dba tablesb) User Table space :: This data file stores all the user related tables We should have seperate table spaces for storing the tables and indexes so that the access is fast.Data Files :: Every Oracle Data Base has one or more physical data files.They store the data for the database.Every datafile is associated with only one database.Once the Data file is created the size cannot change.To increase the size of the database to store more data we have to add data file. Parameter Files :: Parameter file is needed to start an instance.A parameter file contains the list of instance configuration parameters e.g.::db_block_buffers = 500db_name = ORA7db_domain = u.s.acme langControl Files :: Control files record the physical structure of the data files and redo log filesThey contain the Db name, name and location of dbs, data files ,redo log files and time stamp.

616. Physical Storage of the Data
The finest level of granularity of the data base are the data blocks.Data Block :: One Data Block correspond to specific number of physical database spaceExtent :: Extent is the number of specific number of contigious data blocks.Segments :: Set of Extents allocated for Extents. There are three types of Segmentsa) Data Segment :: Non Clustered Table has data segment data of every table is stored in cluster data segmentb) Index Segment :: Each Index has index segment that stores datac) Roll Back Segment :: Temporarily store 'undo' information

617. What are the Pct Free and Pct Used
Pct Free is used to denote the percentage of the free space that is to be left when creating a table. Similarly Pct Used is used to denote the percentage of the used space that is to be used when creating a tableeg.:: Pctfree 20, Pctused 40

618. What is Row Chaining
The data of a row in a table may not be able to fit the same data block.Data for row is stored in a chain of data blocks .

619. What is a 2 Phase Commit
Two Phase commit is used in distributed data base systems. This is useful to maintain the integrity of the database so that all the users see the same values. It contains DML statements or Remote Procedural calls that reference a remote object. There are basically 2 phases in a 2 phase commit.a) Prepare Phase :: Global coordinator asks participants to prepareb) Commit Phase :: Commit all participants to coordinator to Prepared, Read only or abort Reply

620. What is the difference between deleting and truncating of tables
Deleting a table will not remove the rows from the table but entry is there in the database dictionary and it can be retrieved But truncating a table deletes it completely and it cannot be retrieved.

621. What are mutating tables
When a table is in state of transition it is said to be mutating. eg :: If a row has been deleted then the table is said to be mutating and no operations can be done on the table except select.

622. What are Codd Rules
Codd Rules describe the ideal nature of a RDBMS. No RDBMS satisfies all the 12 codd rules and Oracle Satisfies 11 of the 12 rules and is the only Rdbms to satisfy the maximum number of rules.

623. What is Normalisation
Normalisation is the process of organising the tables to remove the redundancy.There are mainly 5 Normalisation rules.a) 1 Normal Form :: A table is said to be in 1st Normal Form when the attributes are atomicb) 2 Normal Form :: A table is said to be in 2nd Normal Form when all the candidate keys are dependant on the primary keyc) 3rd Normal Form :: A table is said to be third Normal form when it is not dependant transitively

624. What is the Difference between a post query and a pre query
A post query will fire for every row that is fetched but the pre query will fire only once.

625. Deleting the Duplicate rows in the table
We can delete the duplicate rows in the table by using the Rowid

626. Can U disable database trigger? How?
Yes. With respect to tableALTER TABLE TABLE [[ DISABLE all_trigger ]]

627. What is pseudo columns ? Name them?
A pseudocolumn behaves like a table column, but is not actually stored in the table. You can select from pseudocolumns, but you cannot insert, update, or delete their values. This section describes these pseudocolumns: * CURRVAL * NEXTVAL * LEVEL * ROWID * ROWNUM

628. How many columns can table have?
The number of columns in a table can range from 1 to 254.

629. Is space acquired in blocks or extents ?
In extents .

630. what is clustered index?
In an indexed cluster, rows are stored together based on their cluster key values . Can not applied for HASH.

631. what are the datatypes supported By oracle (INTERNAL)?
Varchar2, Number,Char , MLSLABEL.

632. What are attributes of cursor?
%FOUND , %NOTFOUND , %ISOPEN,%ROWCOUNT

633. Can you use select in FROM clause of SQL select ?
Yes.

634. Which trigger are created when master -detail rela?
master delete property* NON-ISOLATED (default)a) on check delete masterb) on clear detailsc) on populate details* ISOLATEDa) on clear detailsb) on populate details* CASCADEa) per-deleteb) on clear detailsc) on populate details

635. which system variables can be set by users?
SYSTEM.MESSAGE_LEVELSYSTEM.DATE_THRESHOLDSYSTEM.EFFECTIVE_DATESYSTEM.SUPPRESS_WORKING

636. What are object group?
An object group is a container for a group of objects. You define an object group when you want to package related objects so you can copy or reference them in another module.

637. What are referenced objects?
Referencing allows you to create objects that inherit their functionality and appearance from other objects. Referencing an object is similar to copying an object, except that the resulting reference object maintains a link to its source object. A reference object automatically inherits any changes that have been made to the source object when you open or regenerate the module that contains the reference object.

638. Can you store objects in library?
Referencing allows you to create objects that inherit their functionality and appearance from other objects. Referencing an object is similar to copying an object, except that the resulting reference object maintains a link to its source object. A reference object automatically inherits any changes that have been made to the source object when you open or regenerate the module that contains the reference object.

639. Is forms 4.5 object oriented tool ? why?
yes , partially. 1) PROPERTY CLASS - inheritance property 2) OVERLOADING : procedures and functions.

640. Can you issue DDL in forms?
yes, but you have to use FORMS_DDL.Referencing allows you to create objects that inherit their functionality and appearance from other objects. Referencing an object is similar to copying an object, except that the resulting reference object maintains a link to its source object. A reference object automatically inherits any changes that have been made to the source object when you open or regenerate the module that contains the reference object. Any string expression up to 32K: - a literal - an expression or a variable representing the text of a block of dynamically created PL/SQL code - a DML statement or - a DDL statement Restrictions:The statement you pass to FORMS_DDL may not contain bind variable references in the string, but the values of bind variables can be concatenated into the string before passing the result to FORMS_DDL.

641. What is SECURE property?
- Hides characters that the operator types into the text item. This setting is typically used for password protection.

642. What are the types of triggers and how the sequence of firing in text item
Triggers can be classified as Key Triggers, Mouse Triggers ,Navigational Triggers. Key Triggers :: Key Triggers are fired as a result of Key action.e.g :: Key-next-field, Key-up,Key-DownMouse Triggers :: Mouse Triggers are fired as a result of the mouse navigation.e.g. When-mouse-button-presed,when-mouse-doubleclicked,etcNavigational Triggers :: These Triggers are fired as a result of Navigation. E.g : Post-Text-item,Pre-text-item.We also have event triggers like when ?new-form-instance and when-new-block-instance.We cannot call restricted procedures like go_to(?my_block.first_item?) in the Navigational triggersBut can use them in the Key-next-item.The Difference between Key-next and Post-Text is an very important question. The key-next is fired as a result of the key action while the post text is fired as a result of the mouse movement. Key next will not fire unless there is a key event. The sequence of firing in a text item are as follows ::a) pre - textb) when new item c) key-nextd) when validate e) post text

643. Can you store pictures in database? How?
Yes , in long Raw datatype.

644. What are property classes ? Can property classes have trigger?
Property class inheritance is a powerful feature that allows you to quickly define objects that conform to your own interface and functionality standards. Property classes also allow you to make global changes to applications quickly. By simply changing the definition of a property class, you can change the definition of all objects that inherit properties from that class. Yes . All type of triggers .

677. What is Log Switch ?
The point at which ORACLE ends writing to one online redo log file and begins writing to another is called a log switch.

678. What is On-line Redo Log?
The On-line Redo Log is a set of tow or more on-line redo files that record all committed changes made to the database. Whenever a transaction is committed, the corresponding redo entries temporarily stores in redo log buffers of the SGA are written to an on-line redo log file by the background process LGWR. The on-line redo log files are used in cyclical fashion.

679. Which parameter specified in the DEFAULT STORAGE clause of CREATE TABLESPACE cannot be altered after creating the tablespace?
All the default storage parameters defined for the tablespace can be changed using the ALTER TABLESPACE command. When objects are created their INITIAL and MINEXTENS values cannot be changed.

680. What are the steps involved in Database Startup ?
Start an instance, Mount the Database and Open the Database.

< ? Recovery Instance in involved steps the are What>
Rolling forward to recover data that has not been recorded in data files, yet has been recorded in the on-line redo log, including the contents of rollback segments. Rolling back transactions that have been explicitly rolled back or have not been committed as indicated by the rollback segments regenerated in step a. Releasing any resources (locks) held by transactions in process at the time of the failure. Resolving any pending distributed transactions undergoing a two-phase commit at the time of the instance failure.

682. Can Full Backup be performed when the database is open ?
No.

683. What are the different modes of mounting a Database with the Parallel Server ?
Exclusive Mode If the first instance that mounts a database does so in exclusive mode, only that Instance can mount the database.Parallel Mode If the first instance that mounts a database is started in parallel mode, other instances that are started in parallel mode can also mount the database.

684. What are the advantages of operating a database in ARCHIVELOG mode over operating it in NO ARCHIVELOG mode ?
Complete database recovery from disk failure is possible only in ARCHIVELOG mode. Online database backup is possible only in ARCHIVELOG mode.

685. What are the steps involved in Database Shutdown ?
Close the Database, Dismount the Database and Shutdown the Instance.

686. What is Archived Redo Log ?
Archived Redo Log consists of Redo Log files that have archived before being reused.

687. What is Restricted Mode of Instance Startup ?
An instance can be started in (or later altered to be in) restricted mode so that when the database is open connections are limited only to those whose user accounts have been granted the RESTRICTED SESSION system privilege.

688.. What is a Synonym ?
A synonym is an alias for a table, view, sequence or program unit.

689. What is a Sequence ?
A sequence generates a serial list of unique numbers for numerical columns of a database's tables.

690. What is a Segment ?
A segment is a set of extents allocated for a certain logical structure.

691. What is schema?
A schema is collection of database objects of a User.

692. Describe Referential Integrity ?
A rule defined on a column (or set of columns) in one table that allows the insert or update of a row only if the value for the column or set of columns (the dependent value) matches a value in a column of a related table (the referenced value). It also specifies the type of data manipulation allowed on referenced data and the action to be performed on dependent data as a result of any action on referenced data.

693. What is Hash Cluster ?
A row is stored in a hash cluster based on the result of applying a hash function to the row's cluster key value. All rows with the same hash key value are stores together on disk.

694. What is a Private Synonyms ?
A Private Synonyms can be accessed only by the owner.

695. What is Database Link ?
A database link is a named object that describes a "path" from one database to another.
696. What is index cluster?
A cluster with an index on the cluster key.

697.What is hash cluster?
A row is stored in a hash cluster based on the result of applying a hash function to the row's cluster key value. All rows with the same hash key value are stores together on disk.

698.When can hash cluster used?
Hash clusters are better choice when a table is often queried with equality queries. For such queries the specified cluster key value is hashed. The resulting hash key value points directly to the area on disk that stores the specified rows.

699.When can hash cluster used?
Hash clusters are better choice when a table is often queried with equality queries. For such queries the specified cluster key value is hashed. The resulting hash key value points directly to the area on disk that stores the specified rows.

700. What are the types of database links?
Private database link, public database link & network database link.

701. What is private database link?
Private database link is created on behalf of a specific user. A private database link can be used only when the owner of the link specifies a global object name in a SQL statement or in the definition of the owner's views or procedures.

702. What is public database link?
Public database link is created for the special user group PUBLIC. A public database link can be used when any user in the associated database specifies a global object name in a SQL statement or object definition.

703. What is network database link?
Network database link is created and managed by a network domain service. A network database link can be used when any user of any database in the network specifies a global object name in a SQL statement or object definition.

704. What is data block?
Oracle database's data is stored in data blocks. One data block corresponds to a specific number of bytes of physical database space on disk.

705. How to define data block size?
A data block size is specified for each Oracle database when the database is created. A database users and allocated free database space in Oracle data blocks. Block size is specified in init.ora file and cannot be changed latter.

706. What is row chaining?
In circumstances, all of the data for a row in a table may not be able to fit in the same data block. When this occurs, the data for the row is stored in a chain of data block (one or more) reserved for that segment.

707. What is an extent?
An extent is a specific number of contiguous data blocks, obtained in a single allocation and used to store a specific type of information.

708. What are the different types of segments?
Data segment, index segment, rollback segment and temporary segment.

709. What is a data segment?
Each non-clustered table has a data segment. All of the table's data is stored in the extents of its data segment. Each cluster has a data segment. The data of every table in the cluster is stored in the cluster's data segment.

709. What is an index segment?
Each index has an index segment that stores all of its data.

710. What is rollback segment?
A database contains one or more rollback segments to temporarily store "undo" information.

711. What are the uses of rollback segment?
To generate read-consistent database information during database recovery and to rollback uncommitted transactions by the users.

712. What is a temporary segment?
Temporary segments are created by Oracle when a SQL statement needs a temporary work area to complete execution. When the statement finishes execution, the temporary segment extents are released to the system for future use.

713. What is a datafile?
Every Oracle database has one or more physical data files. A database's data files contain all the database data. The data of logical database structures such as tables and indexes is physically stored in the data files allocated for a database.

714. What are the characteristics of data files?
A data file can be associated with only one database. Once created a data file can't change size. One or more data files form a logical unit of database storage called a tablespace.

715. What is a redo log?
The set of redo log files for a database is collectively known as the database redo log.

716. What is the function of redo log?
The primary function of the redo log is to record all changes made to data.

717. What is the use of redo log information?
The information in a redo log file is used only to recover the database from a system or media failure prevents database data from being written to a database's data files.

718. What does a control file contains?
- Database name- Names and locations of a database's files and redolog files.- Time stamp of database creation.

719. What is the use of control file?
When an instance of an Oracle database is started, its control file is used to identify the database and redo log files that must be opened for database operation to proceed. It is also used in database recovery.

730. Explain the difference between a hot backup and a cold backup and the benefits associated with each.
A hot backup is basically taking a backup of the database while it is still up and running and it must be in archive log mode. A cold backup is taking a backup of the database while it is shut down and does not require being in archive log mode. The benefit of taking a hot backup is that the database is still available for use while the backup is occurring and you can recover the database to any point in time. The benefit of taking a cold backup is that it is typically easier to administer the backup and recovery process. In addition, since you are taking cold backups the database does not require being in archive log mode and thus there will be a slight performance gain as the database is not cutting archive logs to disk.

731. You have just had to restore from backup and do not have any control files. How would you go about bringing up this database?
I would create a text based backup control file, stipulating where on disk all the data files where and then issue the recover command with the using backup control file clause.

732. How do you switch from an init.ora file to a spfile?
Issue the create spfile from pfile command.

732. Explain the difference between a data block, an extent and a segment.
A data block is the smallest unit of logical storage for a database object. As objects grow they take chunks of additional storage that are composed of contiguous data blocks. These groupings of contiguous data blocks are called extents. All the extents that an object takes when grouped together are considered the segment of the database object.

733. Give two examples of how you might determine the structure of the table DEPT.
Use the describe command or use the dbms_metadata.get_ddl package.

734. Where would you look for errors from the database engine?
In the alert log.

735. Compare and contrast TRUNCATE and DELETE for a table.
Both the truncate and delete command have the desired outcome of getting rid of all the rows in a table. The difference between the two is that the truncate command is a DDL operation and just moves the high water mark and produces a now rollback. The delete command, on the other hand, is a DML operation, which will produce a rollback and thus take longer to complete.

736. Give the reasoning behind using an index.
Faster access to data blocks in a table.

737. Give the two types of tables involved in producing a star schema and the type of data they hold.
Fact tables and dimension tables. A fact table contains measurements while dimension tables will contain data that will help describe the fact tables.

738. What type of index should you use on a fact table?
A Bitmap index.

739. Give two examples of referential integrity constraints.
A primary key and a foreign key.

740. A table is classified as a parent table and you want to drop and re-create it. How would you do this without affecting the children tables?
Disable the foreign key constraint to the parent, drop the table, re-create the table, enable the foreign key constraint.

741. Explain the difference between ARCHIVELOG mode and NOARCHIVELOG mode and the benefits and disadvantages to each.
ARCHIVELOG mode is a mode that you can put the database in for creating a backup of all transactions that have occurred in the database so that you can recover to any point in time. NOARCHIVELOG mode is basically the absence of ARCHIVELOG mode and has the disadvantage of not being able to recover to any point in time. NOARCHIVELOG mode does have the advantage of not having to write transactions to an archive log and thus increases the performance of the database slightly.

742. What command would you use to create a backup control file?
Alter database backup control file to trace.

743. Give the stages of instance startup to a usable state where normal users may access it.
STARTUP NOMOUNT - Instance startupSTARTUP MOUNT - The database is mountedSTARTUP OPEN - The database is opened

744. What column differentiates the V$ views to the GV$ views and how?
The INST_ID column which indicates the instance in a RAC environment the information came from.

745. How would you go about generating an EXPLAIN plan?
Create a plan table with utlxplan.sql.Use the explain plan set statement_id = 'tst1' into plan_table for a SQL statementLook at the explain plan with utlxplp.sql or utlxpls.sql

746. How would you go about increasing the buffer cache hit ratio?
Use the buffer cache advisory over a given workload and then query the v$db_cache_advice table. If a change was necessary then I would use the alter system set db_cache_size command.

747. Explain an ORA-01555
You get this error when you get a snapshot too old within rollback. It can usually be solved by increasing the undo retention or increasing the size of rollbacks. You should also look at the logic involved in the application getting the error message.

748. Explain the difference between $ORACLE_HOME and $ORACLE_BASE.
ORACLE_BASE is the root directory for oracle. ORACLE_HOME located beneath ORACLE_BASE is where the oracle products reside.

749. How would you determine the time zone under which a database was operating?
select DBTIMEZONE from dual;

750. Explain the use of setting GLOBAL_NAMES equal to TRUE.
Setting GLOBAL_NAMES dictates how you might connect to a database. This variable is either TRUE or FALSE and if it is set to TRUE it enforces database links to have the same name as the remote database to which they are linking.

751. What command would you use to encrypt a PL/SQL application?
WRAP

752. Explain the difference between a FUNCTION, PROCEDURE and PACKAGE.
A function and procedure are the same in that they are intended to be a collection of PL/SQL code that carries a single task. While a procedure does not have to return any values to the calling application, a function will return a single value. A package on the other hand is a collection of functions and procedures that are grouped together based on their commonality to a business function or application.

753. Explain the use of table functions.
Table functions are designed to return a set of rows through PL/SQL logic but are intended to be used as a normal table or view in a SQL statement. They are also used to pipeline information in an ETL process.

754. Name three advisory statistics you can collect.
Buffer Cache Advice, Segment Level Statistics, & Timed Statistics

755. Where in the Oracle directory tree structure are audit traces placed?
In unix $ORACLE_HOME/rdbms/audit, in Windows the event viewer

756. Explain materialized views and how they are used.
Materialized views are objects that are reduced sets of information that have been summarized, grouped, or aggregated from base tables. They are typically used in data warehouse or decision support systems.

757. When a user process fails, what background process cleans up after it?
PMON

758. What background process refreshes materialized views?
The Job Queue Processes.

759. How would you determine what sessions are connected and what resources they are waiting for?
Use of V$SESSION and V$SESSION_WAIT

760. Describe what redo logs are.
Redo logs are logical and physical structures that are designed to hold all the changes made to a database and are intended to aid in the recovery of a database.

761. How would you force a log switch?
ALTER SYSTEM SWITCH LOGFILE;

762. Give two methods you could use to determine what DDL changes have been made.
You could use Logminer or Streams

763. What does coalescing a tablespace do?
Coalescing is only valid for dictionary-managed tablespaces and de-fragments space by combining neighboring free extents into large single extents.

764. What is the difference between a TEMPORARY tablespace and a PERMANENT tablespace?
A temporary tablespace is used for temporary objects such as sort structures while permanent tablespaces are used to store those objects meant to be used as the true objects of the database.

765. Name a tablespace automatically created when you create a database.
The SYSTEM tablespace.
766. When creating a user, what permissions must you grant to allow them to connect to the database?
Grant the CONNECT to the user.

767. How do you add a data file to a tablespace
ALTER TABLESPACE ADD DATAFILE SIZE

768. How do you resize a data file?
ALTER DATABASE DATAFILE RESIZE ;

769. What view would you use to look at the size of a data file?
DBA_DATA_FILES

770. What view would you use to determine free space in a tablespace?
DBA_FREE_SPACE

771. How would you determine who has added a row to a table?
Turn on fine grain auditing for the table.

772. How can you rebuild an index?
ALTER INDEX REBUILD;

773. Explain what partitioning is and what its benefit is.
Partitioning is a method of taking large tables and indexes and splitting them into smaller, more manageable pieces.

774. You have just compiled a PL/SQL package but got errors, how would you view the errors?
SHOW ERRORS

775. How can you gather statistics on a table?
The ANALYZE command.

776. How can you enable a trace for a session?
Use the DBMS_SESSION.SET_SQL_TRACE orUse ALTER SESSION SET SQL_TRACE = TRUE;

777. What is the difference between the SQL*Loader and IMPORT utilities?
These two Oracle utilities are used for loading data into the database. The difference is that the import utility relies on the data being produced by another Oracle utility EXPORT while the SQL*Loader utility allows data to be loaded that has been produced by other utilities from different data sources just so long as it conforms to ASCII formatted or delimited files.

778. Name two files used for network connection to a database.
TNSNAMES.ORA and SQLNET.ORA

779. What is the function of Optimizer ?
The goal of the optimizer is to choose the most efficient way to execute a SQL statement.

780. What is Execution Plan ?
The combinations of the steps the optimizer chooses to execute a statement is called an execution plan.

781. What is SAVE POINT ?
For long transactions that contain many SQL statements, intermediate markers or savepoints can be declared which can be used to divide a transaction into smaller parts. This allows the option of later rolling back all work performed from the current point in the transaction to a declared savepoint within the transaction.

782. What are the values that can be specified for OPTIMIZER MODE Parameter ?
COST and RULE.

783. Can one resize tablespaces and data files? (for DBA)
One can manually increase or decrease the size of a datafile from Oracle 7.2 using the command.ALTER DATABASE DATAFILE 'filename2' RESIZE 100M;Because you can change the sizes of datafiles, you can add more space to your database without adding more datafiles. This is beneficial if you are concerned about reaching the maximum number of datafiles allowed in your database. Manually reducing the sizes of datafiles allows you to reclaim unused space in the database. This is useful for correcting errors in estimations of space requirements. Also, datafiles can be allowed to automatically extend if more space is required. Look at the following command: CREATE TABLESPACE pcs_data_tsDATAFILE 'c:\ora_apps\pcs\pcsdata1.dbf' SIZE 3MAUTOEXTEND ON NEXT 1M MAXSIZE UNLIMITEDDEFAULT STORAGE (INITIAL 10240NEXT 10240MINEXTENTS 1MAXEXTENTS UNLIMITEDPCTINCREASE 0)ONLINEPERMANENT;

784. Can one rename a tablespace? (for DBA)
No, this is listed as Enhancement Request 148742. Workaround: Export all of the objects from the tablespaceDrop the tablespace including contentsRecreate the tablespaceImport the objects

785. What is RULE-based approach to optimization ?
Choosing an executing planbased on the access paths available and the ranks of these access paths.

786. What are the values that can be specified for OPTIMIZER_GOAL parameter of the ALTER SESSION Command ? )
CHOOSE,ALL_ROWS,FIRST_ROWS and RULE.

787. How does one create a standby database? (for DBA)
While your production database is running, take an (image copy) backup and restore it on duplicate hardware. Note that an export will not work!!! On your standby database, issue the following commands: ALTER DATABASE CREATE STANDBY CONTROLFILE AS 'filename';ALTER DATABASE MOUNT STANDBY DATABASE;RECOVER STANDBY DATABASE;On systems prior to Oracle 8i, write a job to copy archived redo log files from the primary database to the standby system, and apply the redo log files to the standby database (pipe it). Remember the database is recovering and will prompt you for the next log file to apply. Oracle 8i onwards provide an "Automated Standby Database" feature, which will send archived, log files to the remote site via NET8, and apply then to the standby database. When one needs to activate the standby database, stop the recovery process and activate it: ALTER DATABASE ACTIVATE STANDBY DATABASE;

788.How does one give developers access to trace files (required as input to tkprof)? (for DBA)
The "alter session set sql_trace=true" command generates trace files in USER_DUMP_DEST that can be used by developers as input to tkprof. On Unix the default file mask for these files are "rwx r-- ---". There is an undocumented INIT.ORA parameter that will allow everyone to read (rwx r-r--) these trace files:_trace_files_public = trueInclude this in your INIT.ORA file and bounce your database for it to take effect.

789. What are the responsibilities of a Database Administrator ?
Installing and upgrading the Oracle Server and application tools. Allocating system storage and planning future storage requirements for the database system. Managing primary database structures (tablespaces) Managing primary objects (table,views,indexes) Enrolling users and maintaining system security. Ensuring compliance with Oralce license agreement Controlling and monitoring user access to the database. Monitoring and optimizing the performance of the database. Planning for backup and recovery of database information. Maintain archived data on tape Backing up and restoring the database. Contacting Oracle Corporation for technical support.

790. What is a trace file and how is it created ?
Each server and background process can write an associated trace file. When an internal error is detected by a process or user process, it dumps information about the error to its trace. This can be used for tuning the database.

791. What are the roles and user accounts created automatically with the database?
DBA - role Contains all database system privileges.SYS user account - The DBA role will be assigned to this account. All of the base tables and views for the database's dictionary are store in this schema and are manipulated only by ORACLE. SYSTEM user account - It has all the system privileges for the database and additional tables and views that display administrative information and internal tables and views used by oracle tools are created using this username.

792. What are the minimum parameters should exist in the parameter file (init.ora) ?
DB NAME - Must set to a text string of no more than 8 characters and it will be stored inside the datafiles, redo log files and control files and control file while database creation.DB_DOMAIN - It is string that specifies the network domain where the database is created. The global database name is identified by setting these parameters(DB_NAME & DB_DOMAIN) CONTORL FILES - List of control filenames of the database. If name is not mentioned then default name will be used. DB_BLOCK_BUFFERS - To determine the no of buffers in the buffer cache in SGA.PROCESSES - To determine number of operating system processes that can be connected to ORACLE concurrently. The value should be 5 (background process) and additional 1 for each user.ROLLBACK_SEGMENTS - List of rollback segments an ORACLE instance acquires at database startup. Also optionally LICENSE_MAX_SESSIONS,LICENSE_SESSION_WARNING and LICENSE_MAX_USERS.
793. Why and when should I backup my database? (for DBA
Backup and recovery is one of the most important aspects of a DBAs job. If you lose your company's data, you could very well lose your job. Hardware and software can always be replaced, but your data may be irreplaceable! Normally one would schedule a hierarchy of daily, weekly and monthly backups, however consult with your users before deciding on a backup schedule. Backup frequency normally depends on the following factors: . Rate of data change/ transaction rate . Database availability/ Can you shutdown for cold backups? . Criticality of the data/ Value of the data to the company . Read-only tablespace needs backing up just once right after you make it read-only . If you are running in archivelog mode you can backup parts of a database over an extended cycle of days . If archive logging is enabled one needs to backup archived log files timeously to prevent database freezes . Etc. Carefully plan backup retention periods. Ensure enough backup media (tapes) are available and that old backups are expired in-time to make media available for new backups. Off-site vaulting is also highly recommended. Frequently test your ability to recover and document all possible scenarios. Remember, it's the little things that will get you. Most failed recoveries are a result of organizational errors and miscommunications.

794. What strategies are available for backing-up an Oracle database? (for DBA
The following methods are valid for backing-up an Oracle database: Export/Import - Exports are "logical" database backups in that they extract logical definitions and data from the database to a file.Cold or Off-line Backups - Shut the database down and backup up ALL data, log, and control files. Hot or On-line Backups - If the databases are available and in ARCHIVELOG mode, set the tablespaces into backup mode and backup their files. Also remember to backup the control files and archived redo log files. RMAN Backups - While the database is off-line or on-line, use the "rman" utility to backup the database. It is advisable to use more than one of these methods to backup your database. For example, if you choose to do on-line database backups, also cover yourself by doing database exports. Also test ALL backup and recovery scenarios carefully. It is better to be save than sorry. Regardless of your strategy, also remember to backup all required software libraries, parameter files, password files, etc. If your database is in ARCGIVELOG mode, you also need to backup archived log files.

795. What is the difference between online and offline backups? (for DBA
A hot backup is a backup performed while the database is online and available for read/write. Except for Oracle exports, one can only do on-line backups when running in ARCHIVELOG mode. A cold backup is a backup performed while the database is off-line and unavailable to its users.

796. What is the difference between restoring and recovering? (for DBA
Restoring involves copying backup files from secondary storage (backup media) to disk. This can be done to replace damaged files or to copy/move a database to a new location. Recovery is the process of applying redo logs to the database to roll it forward. One can roll-forward until a specific point-in-time (before the disaster occurred), or roll-forward until the last transaction recorded in the log files. Sql> connect SYS as SYSDBASql> RECOVER DATABASE UNTIL TIME '2001-03-06:16:00:00' USING BACKUP CONTROLFILE;

797. How does one backup a database using the export utility? (for DBA
Oracle exports are "logical" database backups (not physical) as they extract data and logical definitions from the database into a file. Other backup strategies normally back-up the physical data files.One of the advantages of exports is that one can selectively re-import tables, however one cannot roll-forward from an restored export file. To completely restore a database from an export file one practically needs to recreate the entire database. Always do full system level exports (FULL=YES). Full exports include more information about the database in the export file than user level exports.
812. What tuning indicators can one use? (for DBA
The following high-level tuning indicators can be used to establish if a database is performing optimally or not: . Buffer Cache Hit RatioFormula: Hit Ratio = (Logical Reads - Physical Reads) / Logical ReadsAction: Increase DB_CACHE_SIZE (DB_BLOCK_BUFFERS prior to 9i) to increase hit ratio . Library Cache Hit RatioAction: Increase the SHARED_POOL_SIZE to increase hit ratio

813. What tools/utilities does Oracle provide to assist with performance tuning? (for DBA
Oracle provide the following tools/ utilities to assist with performance monitoring and tuning:. TKProf. UTLBSTAT.SQL and UTLESTAT.SQL - Begin and end stats monitoring. Statspack. Oracle Enterprise Manager - Tuning Pack

814. What is STATSPACK and how does one use it? (for DBA
Statspack is a set of performance monitoring and reporting utilities provided by Oracle from Oracle8i and above. Statspack provides improved BSTAT/ESTAT functionality, though the old BSTAT/ESTAT scripts are still available. For more information about STATSPACK, read the documentation in file $ORACLE_HOME/rdbms/admin/spdoc.txt. Install Statspack: cd $ORACLE_HOME/rdbms/adminsqlplus "/ as sysdba" @spdrop.sql -- Install Statspack -sqlplus "/ as sysdba" @spcreate.sql-- Enter tablespace names when promptedUse Statspack: sqlplus perfstat/perfstatexec statspack.snap; -- Take a performance snapshots exec statspack.snap; o Get a list of snapshotsselect SNAP_ID, SNAP_TIME from STATS$SNAPSHOT; @spreport.sql -- Enter two snapshot id's for difference reportOther Statspack Scripts: . sppurge.sql - Purge a range of Snapshot Id's between the specified begin and end Snap Id's . spauto.sql - Schedule a dbms_job to automate the collection of STATPACK statistics . spcreate.sql - Installs the STATSPACK user, tables and package on a database (Run as SYS). . spdrop.sql - Deinstall STATSPACK from database (Run as SYS) . sppurge.sql - Delete a range of Snapshot Id's from the database . spreport.sql - Report on differences between values recorded in two snapshots . sptrunc.sql - Truncates all data in Statspack tables

815. What are the common RMAN errors (with solutions)? (for DBA
Some of the common RMAN errors are: RMAN-20242: Specification does not match any archivelog in the recovery catalog.Add to RMAN script: sql 'alter system archive log current';RMAN-06089: archived log xyz not found or out of sync with catalogExecute from RMAN: change archivelog all validate;

822. What is mean by Program Global Area (PGA) ?
It is area in memory that is used by a Single Oracle User Process.

823. What is hit ratio ?
It is a measure of well the data cache buffer is handling requests for data. Hit Ratio = (Logical Reads - Physical Reads - Hits Misses)/ Logical Reads.

824. How do u implement the If statement in the Select Statement
We can implement the if statement in the select statement by using the Decode statement. e.g select DECODE (EMP_CAT,'1','First','2','Second'Null); Here the Null is the else statement where null is done .

825. How many types of Exceptions are there
There are 2 types of exceptions. They area) System Exceptionse.g. When no_data_found, When too_many_rowsb) User Defined Exceptionse.g. My_exception exceptionWhen My_exception then

826. What are the inline and the precompiler directives
The inline and precompiler directives detect the values directly

827. How do you use the same lov for 2 columns
We can use the same lov for 2 columns by passing the return values in global values and using the global values in the code

828. How many minimum groups are required for a matrix report
The minimum number of groups in matrix report are 4

829. What is the difference between static and dynamic lov
The static lov contains the predetermined values while the dynamic lov contains values that come at run time

830. How does one manage Oracle database users? (for DBA
Oracle user accounts can be locked, unlocked, forced to choose new passwords, etc. For example, all accounts except SYS and SYSTEM will be locked after creating an Oracle9iDB database using the DB Configuration Assistant (dbca). DBA's must unlock these accounts to make them available to users. Look at these examples: ALTER USER scott ACCOUNT LOCK -- lock a user accountALTER USER scott ACCOUNT UNLOCK; -- unlocks a locked users accountALTER USER scott PASSWORD EXPIRE; -- Force user to choose a new password

831. How does one tune Oracle Wait events? (for DBA
Some wait events from V$SESSION_WAIT and V$SYSTEM_EVENT views:
Event Name:
Tuning Recommendation:
db file sequential read
Tune SQL to do less I/O. Make sure all objects are analyzed. Redistribute I/O across disks.
buffer busy waits
Increase DB_CACHE_SIZE (DB_BLOCK_BUFFERS prior to 9i)/ Analyze contention from SYS.V$BH
log buffer spaces
Increase LOG_BUFFER parameter or move log files to faster disks

832. What is the difference between DBFile Sequential and Scattered Reads?(for DBA
Both "db file sequential read" and "db file scattered read" events signify time waited for I/O read requests to complete. Time is reported in 100's of a second for Oracle 8i releases and below, and 1000's of a second for Oracle 9i and above. Most people confuse these events with each other as they think of how data is read from disk. Instead they should think of how data is read into the SGA buffer cache. db file sequential read: A sequential read operation reads data into contiguous memory (usually a single-block read with p3=1, but can be multiple blocks). Single block I/Os are usually the result of using indexes. This event is also used for rebuilding the controlfile and reading datafile headers (P2=1). In general, this event is indicative of disk contention on index reads. db file scattered read: Similar to db file sequential reads, except that the session is reading multiple data blocks and scatters them into different discontinuous buffers in the SGA. This statistic is NORMALLY indicating disk contention on full table scans. Rarely, data from full table scans could be fitted into a contiguous buffer area, these waits would then show up as sequential reads instead of scattered reads. The following query shows average wait time for sequential versus scattered reads: prompt "AVERAGE WAIT TIME FOR READ REQUESTS"select a.average_wait "SEQ READ", b.average_wait "SCAT READ" from sys.v_$system_event a, sys.v_$system_event bwhere a.event = 'db file sequential read' and b.event = 'db file scattered read';

833. What is the use of PARFILE option in EXP command ?
Name of the parameter file to be passed for export.

834. What is the use of TABLES option in EXP command ?
List of tables should be exported.ze)

835. What is the OPTIMAL parameter?
It is used to set the optimal length of a rollback segment.

836. How does one use ORADEBUG from Server Manager/ SQL*Plus? (for DBA
Execute the "ORADEBUG HELP" command from svrmgrl or sqlplus to obtain a list of valid ORADEBUG commands. Look at these examples: SQLPLUS> REM Trace SQL statements with bind variablesSQLPLUS> oradebug setospid 10121Oracle pid: 91, Unix process pid: 10121, image: oracleorclSQLPLUS> oradebug EVENT 10046 trace name context forever, level 12Statement processed.SQLPLUS> ! vi /app/oracle/admin/orcl/bdump/ora_10121.trcSQLPLUS> REM Trace Process StatisticsSQLPLUS> oradebug setorapid 2Unix process pid: 1436, image: ora_pmon_orclSQLPLUS> oradebug procstatStatement processed.SQLPLUS>> oradebug TRACEFILE_NAME/app/oracle/admin/orcl/bdump/pmon_1436.trcSQLPLUS> REM List semaphores and shared memory segments in useSQLPLUS> oradebug ipcSQLPLUS> REM Dump Error StackSQLPLUS> oradebug setospid SQLPLUS> oradebug event immediate trace name errorstack level 3SQLPLUS> REM Dump Parallel Server DLM locksSQLPLUS> oradebug lkdebug -a convlockSQLPLUS> oradebug lkdebug -a convresSQLPLUS> oradebug lkdebug -r (i.e 0x8066d338 from convres dump)

837. Are there any undocumented commands in Oracle? (for DBA
Sure there are, but it is hard to find them. Look at these examples: From Server Manager (Oracle7.3 and above): ORADEBUG HELPIt looks like one can change memory locations with the ORADEBUG POKE command. Anyone brave enough to test this one for us? Previously this functionality was available with ORADBX (ls -l $ORACLE_HOME/rdbms/lib/oradbx.o; make -f oracle.mk oradbx) SQL*Plus: ALTER SESSION SET CURRENT_SCHEMA = SYS;

843. What is Overloading of procedures ?
The Same procedure name is repeated with parameters of different datatypes and parameters in different positions, varying number of parameters is called overloading of procedures. e.g. DBMS_OUTPUT put_line

844. What are the return values of functions SQLCODE and SQLERRM ? What is Pragma EXECPTION_INIT ? Explain the usage ?
SQLCODE returns the latest code of the error that has occurred.SQLERRM returns the relevant error message of the SQLCODE.

845. What are the datatypes a available in PL/SQL ?
Some scalar data types such as NUMBER, VARCHAR2, DATE, CHAR, LONG, BOOLEAN. Some composite data types such as RECORD & TABLE.

846. What are the two parts of a procedure ?
Procedure Specification and Procedure Body.

847. What is the basic structure of PL/SQL ?
PL/SQL uses block structure as its basic structure. Anonymous blocks or nested blocks can be used in PL/SQL.

848. What is PL/SQL table ?
Objects of type TABLE are called "PL/SQL tables", which are modeled as (but not the same as) database tables, PL/SQL tables use a primary PL/SQL tables can have one column and a primary key. Cursors

849. WHAT IS RMAN ? (for DBA
Recovery Manager is a tool that: manages the process of creating backups and also manages the process of restoring and recovering from them.

850. WHY USE RMAN ? (for DBA
No extra costs …Its available free
?RMAN introduced in Oracle 8 it has become simpler with newer versions and easier than user managed backups
?Proper security
?You are 100% sure your database has been backed up.
?Its contains detail of the backups taken etc in its central repository
Facility for testing validity of backups also commands like crosscheck to check the status of backup.
Faster backups and restores compared to backups without RMAN
RMAN is the only backup tool which supports incremental backups.
Oracle 10g has got further optimized incremental backup which has resulted in improvement of performance during backup and recovery time
Parallel operations are supported
Better querying facility for knowing different details of backup
No extra redo generated when backup is taken..compared to online
backup without RMAN which results in saving of space in hard disk
RMAN an intelligent tool
Maintains repository of backup metadata
Remembers backup set location
Knows what need to backed up
Knows what is required for recovery
Knows what backups are redundant

UNDERSTANDING THE RMAN ARCHITECTUREAn oracle RMAN comprises ofRMAN EXECUTABLE This could be present and fired even through client sideTARGET DATABASE This is the database which needs to be backed up .RECOVERY CATALOG Recovery catalog is optional otherwise backup details are stored in target database controlfile .It is a repository of information queried and updated by Recovery ManagerIt is a schema or user stored in Oracle database. One schema can support many databasesIt contains information about physical schema of target database datafile and archive log ,backup sets and pieces Recovery catalog is a must in following scenarios. In order to store scripts. For tablespace point in time recoveryMedia Management SoftwareMedia Management software is a must if you are using RMAN for storing backup in tape drive directly.Backups in RMANOracle backups in RMAN are of the following typeRMAN complete backup OR RMAN incremental backupThese backups are of RMAN proprietary natureIMAGE COPYThe advantage of uing Image copy is its not in RMAN proprietary format..Backup FormatRMAN backup is not in oracle format but in RMAN format. Oracle backup comprises of backup sets and it consists of backup pieces. Backup sets are logical entity In oracle 9i it gets stored in a default location There are two type of backup sets Datafile backup sets, Archivelog backup sets One more important point of data file backup sets is it do not include empty blocks. A backup set would contain many backup pieces.A single backup piece consists of physical files which are in RMAN proprietary format.Example of taking backup using RMANTaking RMAN BackupIn non archive mode in dos prompt typeRMANYou get the RMAN promptRMAN > Connect TargetConnect to target database : Magic using target database controlfile instead of recovery catalogLets take a simple backup of database in non archive modeshutdown immediate ; - - Shutdowns the databasestartup mountbackup database ;- its start backing the databasealter database open;We can fire the same command in archive log modeAnd whole of datafiles will be backedBackup database plus archivelog;Restoring databaseRestoring database has been made very simple in 9i .It is justRestore database..RMAN has become intelligent to identify which datafiles has to be restoredand the location of backuped up file.Oracle Enhancement for RMAN in 10 GFlash Recovery AreaRight now the price of hard disk is falling. Many dba are taking oracle database backup inside the hard disk itself since it results in lesser mean time between recoverability.The new parameter introduced isDB_RECOVERY_FILE_DEST = /oracle/flash_recovery_areaBy configuring the RMAN RETENTION POLICY the flash recovery area will automatically delete obsolete backups and archive logs that are no longer required based on that configuration Oracle has introduced new features in incremental backupChange Tracking FileOracle 10g has the facility to deliver faster incrementals with the implementation of changed tracking file feature.This will results in faster backups lesser space consumption and also reduces the time needed for daily backupsIncrementally Updated BackupsOracle database 10g Incrementally Updates Backup features merges the image copy of a datafile with RMAN incremental backup. The resulting image copy is now updated with block changes captured by incremental backups.The merging of the image copy and incremental backup is initiated with RMAN recover command. This results in faster recovery.Binary compression technique reduces backup space usage by 50-75%.With the new DURATION option for the RMAN BACKUP command, DBAs can weigh backup performance against system service level requirements. By specifying a duration, RMAN will automatically calculate the appropriate backup rate; in addition, DBAs can optionally specify whether backups should minimize time or system load.New Features in Oem to identify RMAN related backup like backup pieces, backup sets and image copyOracle 9i New features Persistent RMAN ConfigurationA new configure command has been introduced in Oracle 9i , that lets you configure various features including automatic channels, parallelism ,backup options, etc.These automatic allocations and options can be overridden by commands in a RMAN command file.Controlfile Auto backupsThrough this new feature RMAN will automatically perform a controlfile auto backup. after every backup or copy command. Block Media RecoveryIf we can restore a few blocks rather than an entire file we only need few blocks.We even dont need to bring the data file offline.Syntax for it as followsBlock Recover datafile 8 block 22;Configure Backup OptimizationPrior to 9i whenever we backed up database using RMAN our backup also used take backup of read only table spaces which had already been backed up and also the same with archive log too.Now with 9i backup optimization parameter we can prevent repeat backup of read only tablespace and archive log. The command for this is as follows Configure backup optimization onArchive Log failoverIf RMAN cannot read a block in an archived log from a destination. RMAN automatically attempts to read from an alternate location this is called as archive log failoverThere are additional commands likebackup database not backed up since time '31-jan-2002 14:00:00'Do not backup previously backed up files(say a previous backup failed and you want to restart from where it left off).Similar syntax is supported for restoresbackup device sbt backup set all Copy a disk backup to tape(backing up a backupAdditionally it supports. Backup of server parameter file. Parallel operation supported. Extensive reporting available. Scripting. Duplex backup sets. Corrupt block detection. Backup archive logsPitfalls of using RMANPrevious to version Oracle 9i backups were not that easy which means you had to allocate a channel compulsorily to take backup You had to give a run etc . The syntax was a bit complex …RMAN has now become very simple and easy to use..If you changed the location of backup set it is compulsory for you to register it using RMAN or while you are trying to restore backup It resulted in hanging situationsThere is no method to know whether during recovery database restore is going to fail because of missing archive log file.Compulsory Media Management only if using tape backupIncremental backups though used to consume less space used to be slower since it used to read the entire database to find the changed blocks and also They have difficult time streaming the tape device. .Considerable improvement has been made in 10g to optimize the algorithm to handle changed block.ObservationIntroduced in Oracle 8 it has become more powerful and simpler with newer version of Oracle 9 and 10 g.So if you really don't want to miss something critical please start using RMAN.

851. Explain UNION,MINUS,UNION ALL, INTERSECT ?
INTERSECT returns all distinct rows selected by both queries.MINUS - returns all distinct rows selected by the first query but not by the second.UNION - returns all distinct rows selected by either queryUNION ALL - returns all rows selected by either query, including all duplicates.

852. Should the OEM Console be displayed at all times (when there are scheduled jobs)? (for DBA
When a job is submitted the agent will confirm the status of the job. When the status shows up as scheduled, you can close down the OEM console. The processing of the job is managed by the OIA (Oracle Intelligent Agent). The OIA maintains a .jou file in the agent's subdirectory. When the console is launched communication with the Agent is established and the contents of the .jou file (binary) are reported to the console job subsystem. Note that OEM will not be able to send e-mail and paging notifications when the Console is not started.

853. Difference between SUBSTR and INSTR ?
INSTR (String1,String2(n,(m)),INSTR returns the position of the mth occurrence of the string 2 instring1. The search begins from nth position of string1.SUBSTR (String1 n,m)SUBSTR returns a character string of size m in string1, starting from nth position of string1.

854. What kind of jobs can one schedule with OEM? (for DBA
OEM comes with pre-defined jobs like Export, Import, run OS commands, run sql scripts, SQL*Plus commands etc. It also gives you the flexibility of scheduling custom jobs written with the TCL language.

855. What are the pre requisites ?
I. to modify data type of a column ? ii. to add a column with NOT NULL constraint ? To Modify the datatype of a column the column must be empty. to add a column with NOT NULL constrain, the table must be empty.

856. How does one backout events and jobs during maintenance slots? (for DBA
Managemnet and data collection activity can be suspended by imposing a blackout. Look at these examples: agentctl start blackout # Blackout the entrire agentagentctl stop blackout # Resume normal monitoring and managementagentctl start blackout ORCL # Blackout database ORCLagentctl stop blackout ORCL # Resume normal monitoring and managementagentctl start blackout -s jobs -d 00:20 # Blackout jobs for 20 minutes

857. What are the types of SQL Statement ?
Data Definition Language : CREATE,ALTER,DROP,TRUNCATE,REVOKE,NO AUDIT & COMMIT.Data Manipulation Language: INSERT,UPDATE,DELETE,LOCKTABLE,EXPLAIN PLAN & SELECT.Transactional Control:COMMIT & ROLLBACKSession Control: ALTERSESSION & SETROLESystem Control :ALTER SYSTEM.

858. What is the Oracle Intelligent Agent? (for DBA
The Oracle Intelligent Agent (OIA) is an autonomous process that needs to run on a remote node in the network to make the node OEM manageable. The Oracle Intelligent Agent is responsible for: . Discovering targets that can be managed (Database Servers, Net8 Listeners, etc.); . Monitoring of events registered in Enterprise Manager; and . Executing tasks associated with jobs submitted to Enterprise Manager.

859. How does one start the Oracle Intelligent Agent? (for DBA
One needs to start an OIA (Oracle Intelligent Agent) process on all machines that will to be managed via OEM. For OEM 9i and above:agentctl start agentagentctl stop agentFor OEM 2.1 and below:lsnrctl dbsnmp_startlsnrctl dbsnmp_statusOn Windows NT, start the "OracleAgent" Service.If the agent doesn't want to start, ensure your environment variables are set correctly and delete the following files before trying again:1) In $ORACLE_HOME/network/admin: snmp_ro.ora and snmp_rw.ora.2) Also delete ALL files in $ORACLE_HOME/network/agent/.Can one write scripts to send alert messages to the console?Start the OEM console and create a new event. Select option "Enable Unsolicited Event". Select test "Unsolicited Event". When entering the parameters, enter values similar to these: Event Name: /oracle/script/myalertObject: *Severity: *Message: *One can now write the script and invoke the oemevent command to send alerts to the console. Look at this example: oemevent /oracle/script/myalert DESTINATION alert "My custom error message" where DESTINATION is the same value as entered in the "Monitored Destinations" field when you've registered the event in the OEM Console.

860. Where can one get more information about TCL? (for DBA
One can write custom event checking routines for OEM using the TCL (Tool Command Language) language. Check the following sites for more information about TCL: . The Tcl Developer Xchange - download and learn about TCL. OraTCL at Sourceforge - Download the OraTCL package. Tom Poindexter's Tcl Page - Oratcl was originally written by Tom Poindexter

861. Are there any troubleshooting tips for OEM? (for DBA
. Create the OEM repository with a user (which will manage the OEM) and store it in a tablespace that does not share any data with other database users. It is a bad practice to create the repository with SYS and System. . If you are unable to launch the console or there is a communication problem with the intelligent agent (daemon). Ensure OCX files are registered. Type the following in the DOS prompt (the current directory should be $ORACLE_HOME\BIN: C:\Orawin95\Bin> RegSvr32 mmdx32.OCXC:\Orawin95\Bin> RegSvr32 vojt.OCX. If you have a problem starting the Oracle Agent Solution A: Backup the *.Q files and Delete all the *.Q Files ($Oracle_home/network/agent folder) Backup and delete SNMP_RO.ora, SNMP_RW.ora, dbsnmp.ver and services.ora files ($Oracle_Home/network/admin folder) Start the Oracle Agent service. Solution B: Your version of Intelligent Agent could be buggy. Check with Oracle for any available patches. For example, the Intelligent Agent that comes with Oracle 8.0.4 is buggy. Sometimes you get a Failed status for the job that was executed successfully. Check the log to see the results of the execution rather than relying on this status.

862. What is import/export and why does one need it? (for DBA
The Oracle export (EXP) and import (IMP) utilities are used to perform logical database backup and recovery. They are also used to move Oracle data from one machine, database or schema to another. The imp/exp utilities use an Oracle proprietary binary file format and can thus only be used between Oracle databases. One cannot export data and expect to import it into a non-Oracle database. For more information on how to load and unload data from files, read the SQL*Loader FAQ. The export/import utilities are also commonly used to perform the following tasks: . Backup and recovery (small databases only) . Reorganization of data/ Eliminate database fragmentation . Detect database corruption. Ensure that all the data can be read. . Transporting tablespaces between databases . Etc.

863. what is a display item?
Display items are similar to text items but store only fetched or assigned values. Operators cannot navigate to a display item or edit the value it contains.

867. How does one use the import/export utilities? (for DBA
Look for the "imp" and "exp" executables in your $ORACLE_HOME/bin directory. One can run them interactively, using command line parameters, or using parameter files. Look at the imp/exp parameters before starting. These parameters can be listed by executing the following commands: "exp help=yes" or "imp help=yes". The following examples demonstrate how the imp/exp utilities can be used: exp scott/tiger file=emp.dmp log=emp.log tables=emp rows=yes indexes=noexp scott/tiger file=emp.dmp tables=(emp,dept)imp scott/tiger file=emp.dmp full=yesimp scott/tiger file=emp.dmp fromuser=scott touser=scott tables=deptexp userid=scott/tiger@orcl parfile=export.txt... where export.txt contains:BUFFER=100000FILE=account.dmpFULL=nOWNER=scottGRANTS=yCOMPRESS=yNOTE: If you do not like command line utilities, you can import and export data with the "Schema Manager" GUI that ships with Oracle Enterprise Manager (OEM).

868. What are the types of visual attribute settings?
Custom Visual attributes Default visual attributes Named Visual attributes. Window

869. Can one export a subset of a table? (for DBA
From Oracle8i one can use the QUERY= export parameter to selectively unload a subset of the data from a table. Look at this example: exp scott/tiger tables=emp query=\"where deptno=10\"

870. What are the two ways to incorporate images into a oracle forms application?
Boilerplate ImagesImage_items

871. Can one monitor how fast a table is imported? (for DBA
If you need to monitor how fast rows are imported from a running import job, try one of the following methods:Method 1: select substr(sql_text,instr(sql_text,'INTO "'),30) table_name,rows_processed,round((sysdate-to_date(first_load_time,'yyyy-mm-dd hh24:mi:ss'))*24*60,1) minutes,trunc(rows_processed/((sysdate-to_date(first_load_time,'yyyy-mm-dd hh24:mi:ss'))*24*60)) rows_per_minfrom sys.v_$sqlareawhere sql_text like 'INSERT %INTO "%'and command_type = 2and open_versions > 0;For this to work one needs to be on Oracle 7.3 or higher (7.2 might also be OK). If the import has more than one table, this statement will only show information about the current table being imported. Contributed by Osvaldo Ancarola, Bs. As. Argentina. Method 2:Use the FEEDBACK=n import parameter. This command will tell IMP to display a dot for every N rows imported.

872. Can one import tables to a different tablespace? (for DBA
Oracle offers no parameter to specify a different tablespace to import data into. Objects will be re-created in the tablespace they were originally exported from. One can alter this behaviour by following one of these procedures: Pre-create the table(s) in the correct tablespace:. Import the dump file using the INDEXFILE= option . Edit the indexfile. Remove remarks and specify the correct tablespaces. . Run this indexfile against your database, this will create the required tables in the appropriate tablespaces . Import the table(s) with the IGNORE=Y option. Change the default tablespace for the user:. Revoke the "UNLIMITED TABLESPACE" privilege from the user . Revoke the user's quota from the tablespace from where the object was exported. This forces the import utility to create tables in the user's default tablespace. . Make the tablespace to which you want to import the default tablespace for the user . Import the table

875. What is SQL*Loader and what is it used for? (for DBA
SQL*Loader is a bulk loader utility used for moving data from external files into the Oracle database. Its syntax is similar to that of the DB2 Load utility, but comes with more options. SQL*Loader supports various load formats, selective loading, and multi-table loads.

876. How does one use the SQL*Loader utility? (for DBA
One can load data into an Oracle database by using the sqlldr (sqlload on some platforms) utility. Invoke the utility without arguments to get a list of available parameters. Look at the following example: sqlldr scott/tiger control=loader.ctlThis sample control file (loader.ctl) will load an external data file containing delimited data: load datainfile 'c:\data\mydata.csv'into table empfields terminated by "," optionally enclosed by '"' ( empno, empname, sal, deptno )The mydata.csv file may look like this: 10001,"Scott Tiger", 1000, 4010002,"Frank Naude", 500, 20Another Sample control file with in-line data formatted as fix length records. The trick is to specify "*" as the name of the data file, and use BEGINDATA to start the data section in the control file. load datainfile *replaceinto table departments( dept position (02:05) char(4),deptname position (08:27) char(20))begindataCOSC COMPUTER SCIENCEENGL ENGLISH LITERATUREMATH MATHEMATICSPOLY POLITICAL SCIENCE

877. How can a cross product be created?
By selecting the cross products tool and drawing a new group surrounding the base group of the cross products.

878. Is there a SQL*Unloader to download data to a flat file? (for DBA
Oracle does not supply any data unload utilities. However, you can use SQL*Plus to select and format your data and then spool it to a file: set echo off newpage 0 space 0 pagesize 0 feed off head off trimspool onspool oradata.txtselect col1 ',' col2 ',' col3from tab1where col2 = 'XYZ';spool offAlternatively use the UTL_FILE PL/SQL package: rem Remember to update initSID.ora, utl_file_dir='c:\oradata' parameterdeclarefp utl_file.file_type;beginfp := utl_file.fopen('c:\oradata','tab1.txt','w');utl_file.putf(fp, '%s, %s\n', 'TextField', 55);utl_file.fclose(fp);end;/You might also want to investigate third party tools like SQLWays from Ispirer Systems, TOAD from Quest, or ManageIT Fast Unloader from CA to help you unload data from Oracle.

879. Can one load variable and fix length data records? (for DBA
Yes, look at the following control file examples. In the first we will load delimited data (variable length): LOAD DATAINFILE *INTO TABLE load_delimited_dataFIELDS TERMINATED BY "," OPTIONALLY ENCLOSED BY '"'TRAILING NULLCOLS( data1,data2)BEGINDATA11111,AAAAAAAAAA22222,"A,B,C,D,"If you need to load positional data (fixed length), look at the following control file example:LOAD DATAINFILE *INTO TABLE load_positional_data( data1 POSITION(1:5),data2 POSITION(6:15))BEGINDATA11111AAAAAAAAAA22222BBBBBBBBBBCan one skip header records load while loading?Use the "SKIP n" keyword, where n = number of logical rows to skip. Look at this example: LOAD DATAINFILE *INTO TABLE load_positional_dataSKIP 5( data1 POSITION(1:5),data2 POSITION(6:15))BEGINDATA11111AAAAAAAAAA22222BBBBBBBBBB

880. Can one modify data as it loads into the database? (for DBA
Data can be modified as it loads into the Oracle Database. Note that this only applies for the conventional load path and not for direct path loads. LOAD DATAINFILE *INTO TABLE modified_data( rec_no "my_db_sequence.nextval",region CONSTANT '31',time_loaded "to_char(SYSDATE, 'HH24:MI')",data1 POSITION(1:5) ":data1/100",data2 POSITION(6:15) "upper(:data2)",data3 POSITION(16:22)"to_date(:data3, 'YYMMDD')")BEGINDATA11111AAAAAAAAAA99120122222BBBBBBBBBB990112LOAD DATAINFILE 'mail_orders.txt'BADFILE 'bad_orders.txt'APPENDINTO TABLE mailing_listFIELDS TERMINATED BY ","( addr,city,state,zipcode,mailing_addr "decode(:mailing_addr, null, :addr, :mailing_addr)",mailing_city "decode(:mailing_city, null, :city, :mailing_city)",mailing_state)

881.Can one load data into multiple tables at once? (for DBA
Look at the following control file: LOAD DATAINFILE *REPLACEINTO TABLE empWHEN empno != ' '( empno POSITION(1:4) INTEGER EXTERNAL,ename POSITION(6:15) CHAR,deptno POSITION(17:18) CHAR,mgr POSITION(20:23) INTEGER EXTERNAL)INTO TABLE projWHEN projno != ' '( projno POSITION(25:27) INTEGER EXTERNAL,empno POSITION(1:4) INTEGER EXTERNAL)

885. Can one selectively load only the records that one need? (for DBA
Look at this example, (01) is the first character, (30:37) are characters 30 to 37: LOAD DATAINFILE 'mydata.dat' BADFILE 'mydata.bad' DISCARDFILE 'mydata.dis'APPENDINTO TABLE my_selective_tableWHEN (01) <> 'H' and (01) <> 'T' and (30:37) = '19991217'(region CONSTANT '31',service_key POSITION(01:11) INTEGER EXTERNAL,call_b_no POSITION(12:29) CHAR)

886. Can one skip certain columns while loading data? (for DBA
One cannot use POSTION(x:y) with delimited data. Luckily, from Oracle 8i one can specify FILLER columns. FILLER columns are used to skip columns/fields in the load file, ignoring fields that one does not want. Look at this example: -- One cannot use POSTION(x:y) as it is stream data, there are no positional fields-the next field begins after some delimiter, not in column X. --> LOAD DATATRUNCATE INTO TABLE T1FIELDS TERMINATED BY ','( field1,field2 FILLER,field3)

887. How does one load multi-line records? (for DBA
One can create one logical record from multiple physical records using one of the following two clauses: . CONCATENATE: - use when SQL*Loader should combine the same number of physical records together to form one logical record. . CONTINUEIF - use if a condition indicates that multiple records should be treated as one. Eg. by having a '#' character in column 1.

889. How can get SQL*Loader to COMMIT only at the end of the load file? (for DBA
One cannot, but by setting the ROWS= parameter to a large value, committing can be reduced. Make sure you have big rollback segments ready when you use a high value for ROWS=.

890. Can one improve the performance of SQL*Loader? (for DBA
A very simple but easily overlooked hint is not to have any indexes and/or constraints (primary key) on your load tables during the load process. This will significantly slow down load times even with ROWS= set to a high value.Add the following option in the command line: DIRECT=TRUE. This will effectively bypass most of the RDBMS processing. However, there are cases when you can't use direct load. Refer to chapter 8 on Oracle server Utilities manual.Turn off database logging by specifying the UNRECOVERABLE option. This option can only be used with direct data loads. Run multiple load jobs concurrently.

891. How does one use SQL*Loader to load images, sound clips and documents? (for DBA
SQL*Loader can load data from a "primary data file", SDF (Secondary Data file - for loading nested tables and VARRAYs) or LOGFILE. The LOBFILE method provides and easy way to load documents, images and audio clips into BLOB and CLOB columns. Look at this example: Given the following table: CREATE TABLE image_table (image_id NUMBER(5),file_name VARCHAR2(30),image_data BLOB);Control File: LOAD DATAINFILE *INTO TABLE image_tableREPLACEFIELDS TERMINATED BY ','(image_id INTEGER(5),file_name CHAR(30),image_data LOBFILE (file_name) TERMINATED BY EOF)BEGINDATA001,image1.gif002,image2.jpg

892. What is the difference between the conventional and direct path loader? (for DBA
The conventional path loader essentially loads the data by using standard INSERT statements. The direct path loader (DIRECT=TRUE) bypasses much of the logic involved with that, and loads directly into the Oracle data files. More information about the restrictions of direct path loading can be obtained from the Utilities Users Guide.

GENERAL INTERVIEW QUESTIONS (1)
1.What are the various types of Exceptions ?
User defined and Predefined Exceptions.

2.Can we define exceptions twice in same block ?
No.

3.What is the difference between a procedure and a function ?
Functions return a single variable by value whereas procedures do not return any variable by value. Rather they return multiple variables by passing variables by reference through their OUT parameter.

4.Can you have two functions with the same name in a PL/SQL block ?
Yes.

5.Can you have two stored functions with the same name ?
Yes.

6.Can you call a stored function in the constraint of a table ?
No.

7.What are the various types of parameter modes in a procedure ?
IN, OUT AND INOUT.

8.What is Over Loading and what are its restrictions ?
OverLoading means an object performing different functions depending upon the no. of parameters or the data type of the parameters passed to it.

9.Can functions be overloaded ?
Yes.

10.Can 2 functions have same name & input parameters but differ only by return datatype
No.

11.What are the constructs of a procedure, function or a package ?
The constructs of a procedure, function or a package are :variables and constants cursors exceptions

12.Why Create or Replace and not Drop and recreate procedures ?
So that Grants are not dropped.

13.Can you pass parameters in packages ? How ?
Yes. You can pass parameters to procedures or functions in a package.

14.What are the parts of a database trigger ?
The parts of a trigger are: A triggering event or statement A trigger restriction A trigger action

15.What are the various types of database triggers ?
There are 12 types of triggers, they are combination of :Insert, Delete and Update Triggers.Before and After Triggers.Row and Statement Triggers.(3*2*2=12)

16.What is the advantage of a stored procedure over a database trigger ?
We have control over the firing of a stored procedure but we have no control over the firing of a trigger.

17.What is the maximum no. of statements that can be specified in a trigger statement ?
One.

18.Can views be specified in a trigger statement ?
No

19.What are the values of :new and :old in Insert/Delete/Update Triggers ?
INSERT : new = new value, old = NULLDELETE : new = NULL, old = old valueUPDATE : new = new value, old = old value

20.What are cascading triggers? What is the maximum no of cascading triggers at a time?
When a statement in a trigger body causes another trigger to be fired, the triggers are said to be cascading. Max = 32.

21.What are mutating triggers ?
A trigger giving a SELECT on the table on which the trigger is written.

22.What are constraining triggers ?
A trigger giving an Insert/Updat e on a table having referential integrity constraint on the triggering table.

23.Describe Oracle database's physical and logical structure ?
Physical : Data files, Redo Log files, Control file.Logical : Tables, Views, Tablespaces, etc.

24.Can you increase the size of a tablespace ? How ?
Yes, by adding datafiles to it.

26.What is the use of Control files ?
Contains pointers to locations of various data files, redo log files, etc.

27.What is the use of Data Dictionary ?
Used by Oracle to store information about various physical and logical Oracle structures e.g. Tables, Tablespaces, datafiles, etc

28.What are the advantages of clusters ?
Access time reduced for joins.

29.What are the disadvantages of clusters ?
The time for Insert increases.

30.Can Long/Long RAW be clustered ?
No.

31.Can null keys be entered in cluster index, normal index ?
Yes.

32.Can Check constraint be used for self referential integrity ? How ?
Yes. In the CHECK condition for a column of a table, we can reference some other column of the same table and thus enforce self referential integrity.

33.What are the min. extents allocated to a rollback extent ?
Two

34.What are the states of a rollback segment ? What is the difference between partly available and needs recovery ?
The various states of a rollback segment are :ONLINE, OFFLINE, PARTLY AVAILABLE, NEEDS RECOVERY and INVALID.

35.What is the difference between unique key and primary key ?
Unique key can be null; Primary key cannot be null.

36.An insert statement followed by a create table statement followed by rollback ? Will the rows be inserted ?
No.

37.Can you define multiple savepoints ?
Yes.

38.Can you Rollback to any savepoint ?
Yes.

40.What is the maximum no. of columns a table can have ?
254.

41.What is the significance of the & and && operators in PL SQL ?
The & operator means that the PL SQL block requires user input for a variable. The && operator means that the value of this variable should be the same as inputted by the user previously for this same variable. If a transaction is very large, and the rollback segment is not able to hold the rollback information, then will the transaction span across different rollback segments or will it terminate ? It will terminate (Please check ).

42.Can you pass a parameter to a cursor ?
Explicit cursors can take parameters, as the example below shows. A cursor parameter can appear in a query wherever a constant can appear. CURSOR c1 (median IN NUMBER) IS SELECT job, ename FROM emp WHERE sal > median;

43.What are the various types of RollBack Segments ?
Public Available to all instancesPrivate Available to specific instance

44.Can you use %RowCount as a parameter to a cursor ?
Yes

45.Is the query below allowed :Select sal, ename Into x From emp Where ename = 'KING'(Where x is a record of Number(4) and Char(15))
Yes

46.Is the assignment given below allowed :ABC = PQR (Where ABC and PQR are records)
Yes

47.Is this for loop allowed :For x in &Start..&End Loop
Yes

48.How many rows will the following SQL return :Select * from emp Where rownum < rownum =" 10;"> , like '% ...' is NOT functions, field +constant, field ''

79.Assume that there are multiple databases running on one machine. How can you switch from one to another ?
Changing the ORACLE_SID

80.What are the advantages of Oracle ?
Portability : Oracle is ported to more platforms than any of its competitors, running on more than 100 hardware platforms and 20 networking protocols.Market Presence : Oracle is by far the largest RDBMS vendor and spends more on R & D than most of its competitors earn in total revenue. This market clout means that you are unlikely to be left in the lurch by Oracle and there are always lots of third party interfaces available.Backup and Recovery : Oracle provides industrial strength support for on-line backup and recovery and good software fault tolerence to disk failure. You can also do point-in-time recovery.Performance : Speed of a 'tuned' Oracle Database and application is quite good, even with large databases. Oracle can manage > 100GB databases.Multiple database support : Oracle has a superior ability to manage multiple databases within the same transaction using a two-phase commit protocol.

81.What is a forward declaration ? What is its use ?
PL/SQL requires that you declare an identifier before using it. Therefore, you must declare a subprogram before calling it. This declaration at the start of a subprogram is called forward declaration. A forward declaration consists of a subprogram specification terminated by a semicolon.

82.What are actual and formal parameters ?
Actual Parameters : Subprograms pass information using parameters. The variables or expressions referenced in the parameter list of a subprogram call are actual parameters. For example, the following procedure call lists two actual parameters named emp_num and amount:Eg. raise_salary(emp_num, amount);Formal Parameters : The variables declared in a subprogram specification and referenced in the subprogram body are formal parameters. For example, the following procedure declares two formal parameters named emp_id and increase: Eg. PROCEDURE raise_salary (emp_id INTEGER, increase REAL) IS current_salary REAL;

83.What are the types of Notation ?
Position, Named, Mixed and Restrictions.

84.What all important parameters of the init.ora are supposed to be increased if you want to increase the SGA size ?
In our case, db_block_buffers was changed from 60 to 1000 (std values are 60, 550 & 3500) shared_pool_size was changed from 3.5MB to 9MB (std values are 3.5, 5 & 9MB) open_cursors was changed from 200 to 300 (std values are 200 & 300) db_block_size was changed from 2048 (2K) to 4096 (4K) {at the time of database creation}.The initial SGA was around 4MB when the server RAM was 32MB and The new SGA was around 13MB when the server RAM was increased to 128MB.

85.If I have an execute privilege on a procedure in another users schema, can I execute his procedure even though I do not have privileges on the tables within the procedure ?
Yes

86.What are various types of joins ?
Equijoins, Non-equijoins, self join, outer join

87.What is a package cursor ?
A package cursor is a cursor which you declare in the package specification without an SQL statement. The SQL statement for the cursor is attached dynamically at runtime from calling procedures.

88.If you insert a row in a table, then create another table and then say Rollback. In this case will the row be inserted ?
Yes. Because Create table is a DDL which commits automatically as soon as it is executed. The DDL commits the transaction even if the create statement fails internally (eg table already exists error) and not syntactically.

89.What are the various types of queries ??
Normal QueriesSub QueriesCo-related queriesNested queriesCompound queries

90.What is a transaction ?
A transaction is a set of SQL statements between any two COMMIT and ROLLBACK statements.

91.What is implicit cursor and how is it used by Oracle ?
An implicit cursor is a cursor which is internally created by Oracle. It is created by Oracle for each individual SQL.

92.Which of the following is not a schema object : Indexes, tables, public synonyms, triggers and packages ?
Public synonyms

94.What is PL/SQL?
PL/SQL is Oracle's Procedural Language extension to SQL. The language includes object oriented programming techniques such as encapsulation, function overloading, information hiding (all but inheritance), and so, brings state-of-the-art programming to the Oracle database server and a variety of Oracle tools.

95.Is there a PL/SQL Engine in SQL*Plus?
No. Unlike Oracle Forms, SQL*Plus does not have a PL/SQL engine. Thus, all your PL/SQL are send directly to the database engine for execution. This makes it much more efficient as SQL statements are not stripped off and send to the database individually.

96.Is there a limit on the size of a PL/SQL block?
Currently, the maximum parsed/compiled size of a PL/SQL block is 64K and the maximum code size is 100K. You can run the following select statement to query the size of an existing package or procedure.SQL> select * from dba_object_size where name = 'procedure_name'

97.Can one read/write files from PL/SQL?
Included in Oracle 7.3 is a UTL_FILE package that can read and write files. The directory you intend writing to has to be in your INIT.ORA file (see UTL_FILE_DIR=... parameter). Before Oracle 7.3 the only means of writing a file was to use DBMS_OUTPUT with the SQL*Plus SPOOL command.DECLAREfileHandler UTL_FILE.FILE_TYPE;BEGINfileHandler := UTL_FILE.FOPEN('/home/oracle/tmp', 'myoutput','W');UTL_FILE.PUTF(fileHandler, 'Value of func1 is %sn', func1(1));UTL_FILE.FCLOSE(fileHandler);END;

98.How can I protect my PL/SQL source code?
PL/SQL V2.2, available with Oracle7.2, implements a binary wrapper for PL/SQL programs to protect the source code. This is done via a standalone utility that transforms the PL/SQL source code into portable binary object code (somewhat larger than the original). This way you can distribute software without having to worry about exposing your proprietary algorithms and methods. SQL*Plus and SQL*DBA will still understand and know how to execute such scripts. Just be careful, there is no "decode" command available.The syntax is: wrap iname=myscript.sql oname=xxxx.yyy

99.Can one use dynamic SQL within PL/SQL? OR Can you use a DDL in a procedure ? How ?
From PL/SQL V2.1 one can use the DBMS_SQL package to execute dynamic SQL statements. Eg: CREATE OR REPLACE PROCEDURE DYNSQLAScur integer;rc integer;BEGINcur := DBMS_SQL.OPEN_CURSOR;DBMS_SQL.PARSE(cur,'CREATE TABLE X (Y DATE)', DBMS_SQL.NATIVE);rc := DBMS_SQL.EXECUTE(cur);DBMS_SQL.CLOSE_CURSOR(cur);END;

Oracle And Sunil Gahlot

Saturday, March 28, 2009

Monday, June 04, 2007

I Love My Dreams : Sunil

About Me

Blog Archive