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Computer Interview Questions Answers

Oracle Interview Questions Answers

Question - 111 : - What are the ways to monitor the performance of the report?

Answer - 111 : - Use reports profile executable statement. Use SQL trace facility.

Question - 112 : - What is a SQL * NET?

Answer - 112 : - 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.

Question - 113 : - How does one prevent tablespace fragmentation? (for DBA)

Answer - 113 : - 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. E.g.. 100K, 100K, 200K, 400K, etc. 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.

Question - 114 : - Does Oracle write to data files in begin/hot backup mode?

Answer - 114 : - 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.

Question - 115 : - How can one see who is using a temporary segment?

Answer - 115 : - 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$sort_usage. Look at these examples: select s.username, u."USER", u.tablespace, u.contents, u.extents, u.blocks from sys.v_$session s, sys.v_$sort_usage u where s.addr = u.session_addr / select s.osuser, s.process, s.username, s.serial#, Sum (u.blocks)*vp.value/1024 sort_size from sys.v_$session s, sys.v_$sort_usage u, sys.v_$parameter VP where 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 /

Question - 116 : - How to define Data Block size ?

Answer - 116 : - 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 can’t be changed latter.

Question - 117 : - What is a User_exit?

Answer - 117 : - Calls the user exit named in the user_exit_string. Invokes a 3Gl program by name which has been properly linked into your current oracle forms executable.

Question - 118 : - How does one connect to an administrative user?

Answer - 118 : - If an administrative user belongs to the "dba" group on Unix, or the "ORA_DBA" (ORA_sid_DBA) group on NT, he/she can connect like this: connect / as sysdba No password is required. This is equivalent to the desupported "connect internal" method. A password is required for "non-secure" administrative access. These passwords are stored in password files. Remote connections via Net8 are classified as non-secure. Look at this example: connect sys/password as sysdba

Question - 119 : - How does one backup archived log files?

Answer - 119 : - 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> backup 4> format '/app/oracle/arch_backup/log_t%t_s%s_p%p' 5> (archivelog all delete input); 6> release channel dev1; 7> }

Question - 120 : - What are the Characteristics of Data Files ?

Answer - 120 : - 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.

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