Re: RMAN question

From: Jared Still <jkstill_at_gmail.com>
Date: Mon, 17 Sep 2007 19:04:40 -0700
Message-ID: <bf46380709171904y529da7b9y4e905aee27a44b64@mail.gmail.com>

I'll get on my soapbox for this one.

Using RMAN without a Repository Catalog in a separate database (on a separate server!) is a mistake.

Oracle would have you believe that RMAN is just as robust with CF only as it is with a repository.

From ML Note 360416.1 on 10g

Except for stored scripts, all of RMAN's features work equally well with or without a recovery catalog.[1] <#_ftn1>

[1] <#_ftnref1> Don't believe it.

Next see:
ML Note 304305.1 Limitations of TSPITR Without a Recovery Catalog

Database incarnations require an external recovery catalog.

retrieving the DBID of a database is easy with a recovery catalog:

select * from rc_database where lower(name) = 'orcl'

Why would you need the DBID?
To recover an autobackup controlfile.

Of course with a recovery catalog, you don't need to look up the DBID, as RMAN does it for you.

Without a recovery catalog, you must know the DBID to recover an autobackup controlfile.

Experience with different recovery scenarios has shown the a recovery catalog makes many recoveries much easier.

Many difficult recovery scenarios can be done with a CF only, but the expense in doing so comes at recovery time when you are trying to determine what to restore, and how to do the recovery with a CF only.

The restoration of autobackup controlfiles is one example.

A recovery catalog allows you to maintain backup data for long periods of time.

Using Netbackup as an example, even after backup pieces have been removed from the NBU catalog and the tapes have gone offsite, the recovery catalog can
retain that information.

Once the tapes have been re-cataloged in NBU, there's nothing else to do in RMAN
except perform the recovery. This assumes that you do not run CROSSCHECK to sync up RMAN with the NBU catalog.

Leaving that much data in a controlfile can make for some rather large CF's, but no
problems for a recovery catalog.

Why leave backup data in a recovery catalog for long periods of time?

If you delete the information a backup piece from the catalog, putting it back
in is a bit of a pain. The backup piece must be on disk to recatalog it.

So, most things are possible with CF only, but you may not want to rely exclusively on a CF for recovery.

... stepping of the soapbox now

-- 
Jared Still
Certifiable Oracle DBA and Part Time Perl Evangelist

--
http://www.freelists.org/webpage/oracle-l

Received on Mon Sep 17 2007 - 21:04:40 CDT