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Re: Minimizing backup induced downtime

From: <>
Date: Thu, 12 Jul 2007 13:53:08 -0700
Message-ID: <>

On Jul 12, 4:40 pm, Alexander Skwar <> wrote:
> Alexander Skwar <>:
> > <>:
> >> On Thu, 12 Jul 2007 20:55:42 +0200, Alexander Skwar
> >> <> wrote:
> >>>Pray tell, why is it not a backup, if I get back everything I need?
> >> For the umpteenth time. YOU DON"T GET EVERYTHING BACK!!!!
> > Ah, I see. So when I have everything back, I don't have everything
> > back. I see.
> Clarification: When I have everything back, _that_ _I_ _care_ _about_.
> Alexander Skwar
> --
> Algol-60 surely must be regarded as the most important programming language
> yet developed.
> -- T. Cheatham

>Suppose you're doing a RMAN backup at 22:30. At 22:45 it's
>done, ie. also writing to tape is finished at that time.
>At 23:00, the server dies and the tapes are still intact.
>With that magical RMAN thing, how will you be able to recover
>anything that's changed in the database after 22:46? My, maybe
>ncomplete, understanding of how RMAN works, is, that it can
>take a backup of an Oracle database without the need for having
>it shutdown (thus a hot backup). But how will RMAN allow me
>to recover something, which hasn't been backed up?

I've done just such a test and it works magically. I'm beginning to think that you either aren't running in archive log mode, or you don't know what that is. Either way, someday someone will hear you use the word "backup" and assume that you mean "recoverable" when you clearly don't. Your meaning is that you can go back to the last good export, and that's it. If you lose 6 hours of data or 23 hours of data, I suppose your organization can stand the time it takes to either recreate the data, or tolerates the lost data. In most shops, the loss of even one transaction is critical, hence RMAN or even old school hotbackups running in archive redo log mode.

Sooner or later your luck will run out. What if the server dies during your ZFS snapshot or your export? Then you have to go back even farther?

I posted some helpful info in the other thread on places to look for help with RMAN (sample RMAN scripts in $ORACLE_HOME/rdbms/demo) but you clearly did not see that.

In an earlier thread someone gave advice to a newbie DBA of "Don't turn 40." It's not the age, it's the unwillingness to learn and apply the better technology where it's appropriate that wrecks careers. I know many DBAs and systems administrators who are well into their 40s and 50s who are very gainfully employed as they continue to provide value to their employers.

Roger Gorden
Sr. DBA. Skila Corp. Received on Thu Jul 12 2007 - 15:53:08 CDT

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