The RMAN catalog Database contains the MetaData about all the Database backups that are available for the purposes of recovering a given database.

1) Control Files have a limited size - depending on the frequency of your backups, you may find that your control files can not hold enough MetaData to meet your retention policy. e.g. If you want to be able to recover a backup from 1 year ago, you need the MetaData from 1 year ago

2) With the RMAN catalog, you have all the Metadata for all your databases in one place, for as long as you need them. As long as the backups still exist on tape (i.e. they have not been expired out of the tape pool), when RMAN does a recovery, it will consider those backup pieces as being available to perform the restore. Without the MetaData, even if the backup piece was still on tape, RMAN would not know about it and hence could not recover it. If you knew the backup piece name, it may be possible to register the backup piece in the catalog manually, but this would be tedious and error prone to say the least!

The catalog is therefore a vital database. If you did lose it for any reason, but still had all the databases that use this catalog, you can easily create a new one and reregister all your databases. The only catch there is the the MetaData that is loaded into the new catalog would be limited to the RECORD_KEEP_TIME for each database.

Regards,

Paul


*********** ORIGINAL MESSAGE ***********

On 30/03/2005 at 4:05 PM Groot A.F.H. de wrote:

Hi,
Just curious...

Why backup the RMAN catalog?

A. it is there for safety of losing all controlefiles or restoration
beyond a resetlog.
B. if the database(s) is(are) there you can rebuild it easy. ( I have
only 4 but have no idea what the impact is if there are 400 )

Maybe the more experienced DBA can tell me.

Tonny de Groot
DienstenCentrum van:
College voor zorgverzekeringen / College Toezicht Zorgverzekeringen



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