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Re: RMAN - Recover the recovery catalog

From: Howard J. Rogers <hjr_at_dizwell.com>
Date: Mon, 23 Aug 2004 06:22:13 +1000
Message-ID: <4127ae94$0$25605$afc38c87@news.optusnet.com.au>


Latyr wrote:

> Hi
>
> Talking with a friend of mine with some knowledge in Oracle, I have been
> quite surprise to learn that it is possible from Oracle9i to recover the
> RMAN catalog even if it lost completely (DRP).
>
> He told me that with the autobackup controlfile, I may be able to recreate
> the catalog as I can ask rman to recover from the autobackup control file
> and spfile, all the registered database and to recover as well my backup
> et backupset information.
>
> Does anybody knows a link that explain that ?
>
> Thanks

You need to get the terminology straight. Visit http://tahiti.oracle.com to start reading the RMAN documentation. The particular bit you'd be interested in can be found by searching for the phrase 'disaster recovery'. But it sounds like you could benefit from reading more than just that little bit.

The database you backup is called the target database. The OPTIONAL database which records details of which bits of the target you backed up when is known as the catalog database.

If you lose absolutely everything of the TARGET, then controlfile autobackups make it very easy to use RMAN to recover the lot. That's the TARGET being recovered, not the catalog database. In fact, you don't even need the catalog database to be able to do the total target recovery.

And you don't even need the controlfile autobackup to do it. Provided you have a backup of the target's controlfile somewhere (perhaps one you manually made yourself) then the technique will work. Hence, disaster recovery has been possible since 8.0. All controlfile autobackup does is to make it a bit easier.

That said, the catalog database *is* just a database, like any other database. It therefore needs backing up too... at which point it becomes the target, and some other database (presumably) becomes its catalog. If you lost the entire catalog database, then disaster recovery techniques could be used to get it back, too -just as they could be used to recover ANY database which has suffered catastrophic loss, but for which decent backups and archived redo logs exist.

Regards
HJR Received on Sun Aug 22 2004 - 15:22:13 CDT

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