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Re: Database Recovery

From: John P. Higgins <jh33378_at_deere.com>
Date: Mon, 15 Feb 1999 13:40:47 -0600
Message-ID: <36C8783E.A950BA02@deere.com>


I agree.

There is no reason to favor cold backups over hot backups, most of the time.

I do like to shut down and take a cold backup before I do something serious (like upgrade!). In this case, I have no intention of recovering; all I want is to reposition myself prior to the problem.

The other serious thing we do involves occasional mass loads. If I leave archiving on, I will overflow the 6 GB archive destination several times! So, I disable archiving, shut down, cold backup, startup, do the load, enable archiving, shut down, cold backup, startup.

Jeremiah Wilton wrote:

> On Mon, 15 Feb 1999 rprabha_at_my-dejanews.com wrote:
>
> > In a 24X7 environment, a combination of fast restoration of COLD backup
> > on tapes coupled with rolling forward the archive logs works out as a
> > very workable and practical solution.
>
> In a 24X7 environment, how would you have gotten a cold backup in the
> first place?
>
> > Also, a HOT backup is a fuzzy backup and thus it would be unwise to
> > rely solely upon HOT backups.e.g. When applying redo logs, if one of
> > the archive logs turns out to be corrupt, DBA will have to opt for the
> > CANCEL based recovery. Thus odds of point in time recovery
> > become less than the anticipated perfect score.
>
> But aren't you in the same boat with a cold backup? If you don't want to
> lose transactions, you have to roll forward through archived redologs to
> the point your database failed. This is the case with both hot and cold
> backups. I don't see the disadvantage to hot backups, especially if you
> have serious high-availability requirements. It is possible to turn on
> block checksumming on the redologs if you are really worried about redolog
> corruption, but if you are multiplexing your logs across disks and
> controllers the chances of that are remote. Why are people so afraid of
> hot backups?
>
> --
> Jeremiah Wilton http://www.wolfenet.com/~jeremiah
Received on Mon Feb 15 1999 - 13:40:47 CST

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