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ORACLE Interview Questions and Answers
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(Continued from previous part...)
304. How to implement the multiple control files for an existing database ?
Shutdown the database
Copy one of the existing control file to new location
Edit Config ora file by adding new control file. name
Restart the database.
305. What is advantage of having disk shadowing/ Mirroring ?
Shadow set of disks save as a backup in the event of disk failure. In most Operating System if any disk failure occurs it automatically switchover to place of failed disk. Improved performance because most OS support volume shadowing can direct file I/O request to use the shadow set of files instead of the main set of files. This reduces
I/O load on the main set of disks.
306. How will you force database to use particular rollback segment ?
SET TRANSACTION USE ROLLBACK SEGMENT rbs_name.
307. Why query fails sometimes ?
Rollback segment dynamically extent to handle larger transactions entry loads. A single transaction may wipeout all available free space in the Rollback Segment Tablespace. This prevents other user using Rollback segments.
308. What is the use of RECORD LENGTH option in EXP command ?
Record length in bytes.
309. How will you monitor rollback segment status ?
Querying the DBA_ROLLBACK_SEGS view
IN USE - Rollback Segment is on-line.
AVAILABLE - Rollback Segment available but not on-line.
OFF-LINE - Rollback Segment off-line
INVALID - Rollback Segment Dropped.
NEEDS RECOVERY - Contains data but need recovery or corupted.
PARTLY AVAILABLE - Contains data from an unresolved transaction involving a distributed database.
310. What is meant by Redo Log file mirroring ? How it can be achieved?
Process of having a copy of redo log files is called mirroring.
This can be achieved by creating group of log files together, so that LGWR will automatically writes them to all the members of the current on-line redo log group. If any one group fails then database automatically switch over to next group. It degrades performance.
311. Which parameter in Storage clause will reduce no. of rows per block?
PCTFREE parameter
Row size also reduces no of rows per block.
312. What is meant by recursive hints ?
Number of times processes repeatedly query the dictionary table is called recursive hints. It is due to the data dictionary cache is too small. By increasing the SHARED_POOL_SIZE parameter we can optimize the size of Data Dictionary Cache.
313. What is the use of PARFILE option in EXP command ?
Name of the parameter file to be passed for export.
(Continued on next part...)
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