Re: [oracle-l] rman catalog considerations

From: Tim Gorman <tim_at_sagelogix.com>
Date: Thu, 29 Jan 2004 21:04:22 -0700
Message-ID: <BC3F25D6.F5C3%tim@sagelogix.com>

In this ³mutual supporting² configuration,you don¹t 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:

storing information for periods of time longer than CONTROLFILE_RECORD_KEEP_TIME
> * retaining information about READ ONLY tablespaces archived for months or
> years
storing information across RESETLOGS
> * to allow recovery across RESETLOGS
centralizing RMAN information from two or more ³target² databases
> * redundant backup of information stored in the controlfile

NOCATALOG isn¹t 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. I¹ve always taken controlfile backups redundantly during backups (one copy to disk as well as tape), and 9i¹s 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:

now there is another database to manage and backup
upgrades from one version of RDBMS to another requires upgrade of the corresponding ³recovery catalog² repository

If you don¹t 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 hanksdc_at_about-inc.com 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