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Re: [oracle-l] rman catalog considerations

From: Tim Gorman <>
Date: Thu, 29 Jan 2004 21:04:22 -0700
Message-ID: <>

In this ³mutual supporting² configuration,you donıt need additional instances just to house the ³recovery catalog² database? Your idea to house them inside the ³business² instances is quite viable, as the RMAN ³recovery catalog² is a very low-usage, low-traffic database application.

May I ask a quick question: why do you need to have a "recovery catalog" database at all?

Running RMAN in "nocatalog" mode has exactly the same functionality as running it with a "recovery catalog" database tacked on. Reasons for using a ³recovery catalog² database instead of NOCATALOG:

NOCATALOG isnıt as risky as one might think. It is easy and very natural to be super-paranoid about controlfile backups ‹ flying NOCATALOG airlines just gives another reason. Iıve always taken controlfile backups redundantly during backups (one copy to disk as well as tape), and 9iıs CONFIGURE CONTROLFILE AUTOBACKUP just makes it easier.

I think most people assume that a ³recovery catalog² is required or even a strongly recommended part of RMAN. In reality, it is just an option that is available for very specific reasons. And, like many such options, it comes at a cost in extra complexity:

If you donıt intend to store recovery information for very long (i.e. Less than 30 days), then you should really consider NOCATALOG.

Just my $0.02 (let the stone-throwing begin)...

on 1/23/04 2:33 PM, Daniel Hanks at wrote:

> I'm in the process of revamping my backup procedures, and had some ideas I
> wanted to filter through the wisdom/experience of the list.
> In my current setup, I have two main database machines, let's call them M1,
> and M2.
> - On M1, I have 2 instances, one 'business' instance, and 1 instance which
> serves as the recovery catalog for M2 (total of 2 instances).
> - On M2 I have 2 'business' instances, and 1 instance which serves as the
> recovery catalog for M1 (total of 3 instances).
> So essentially M1 hosts the recovery catalog for the databases on M2, and
> likewise M2 hosts the recovery catalog for the database on M1.
> My question is, would it be prudent/beneficial to put the recovery catalogs
> into their own schemas in the 'business' instances, instead of maintaining
> them in their own instances?
> Some benefits I see in doing this:
> - That would make 2 less instances I have to concern myself with.
> - I now have (slightly) more memory/resources to allocate to the 'business'
> instances.
> - Backups of the recovery catalogs are now handled by the regular backups of
> the 'business' instances.
> Some drawbacks to doing this:
> - The recovery catalog is now 'coupled' to the business instance. If the
> business instance is down for an extended period of time (which 'should never
> happen'
> :-) then I'd be 'unable' to make rman backups of the other machine at least
> with the catalog.
> - Are there other drawbacks?
> Thanks for your thoughts and suggestions,
> -- Dan
> ========================================================================
> Daniel Hanks - Systems/Database Administrator
> About Inc., Web Services Division
> ========================================================================

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Received on Thu Jan 29 2004 - 22:04:22 CST

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