Set - 4

Question 6 :

What is advantage of having disk shadowing/ Mirroring ?

Answer :

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.


Question 7 :

How will you force database to use particular rollback segment ?

Answer :

SET TRANSACTION USE ROLLBACK SEGMENT rbs_name.


Question 8 :

Why query fails sometimes ?

Answer :

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.


Question 9 :

What is the use of RECORD LENGTH option in EXP command ?

Answer :

Record length in bytes.


Question 10 :

How will you monitor rollback segment status ?

Answer :

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.