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Oracle DBA Interview Questions and answwer-- 5 in oracle

1.This is what happens when we issued "backup validate ;"
RMAN>backup validate X;
Where X is database|tablespace|datafile spec. When using the VALIDATE option:

the WHOLE datafile is fully scanned
no physical backuppiece is written
VALIDATE runtime represents time spent scanning the input files
the difference in runtime between this and the normal backup represents time spent writing to the output device


2.What is the difference between physical and logical backups?
Logical backup implies taking "logical"copies of the database, i.e., the tables, indexes, synonyms, triggers, tablespaces, etc. Physical backup implies taking a "physical" or "actual"backup of the dat...
Logical backup means backup of tablespace in the form of binary but physical backup means backup of databfile, controlfile, logfile, spfile



3.What is the difference between obsolete RMAN backups and expired RMAN backups?
Obsolete: means the backup piece is still available,but it is no longer needed.It depends on retention policy,i,e.recovery window .

Expired: means the backup piece or backup set is not found in the backup destination.

4.Oracle database help us to reduce time for taking backup using followings
1) Oracle performs BLOCKlevel backup.
2) DBA can allocate channels which will start the backup activity in PARALLEL, but we need to ensure that not too many channels have been allocated. Number of allocated channel should not be more than number of CPU.



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