Comments embedded.
HJR
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Resources for Oracle: http://www.hjrdba.com
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"Alex Stankevich" <alex.stankevich_at_redshift-tech.com> wrote in message
news:e8199f5.0112111613.76a1dafb_at_posting.google.com...
> Oracle8i (8.1.6) Backup and Recovery Questions
>
> Here is the situation that I need to address:
>
> All the disks on my server machine are fried and all data is lost. I
> need to restore the machine and Oracle. I do a weekly cold backup of
> Oracle running in ARCHIVELOG mode.
>
> I restore the machine by first restoring a low level disk image of the
> machine just before it went to production (with Oracle already
> installed and setup).
>
> Then to restore Oracle to a recent state, I take the latest cold
> backup of oracle and restore all of its files: control files, data
> files and online redo files.
>
> Then I start Oracle normally: SVRMGRL> startup.
>
> Q1: Would this procedure correctly restore Oracle to a state of the
> cold backup?
>
Yes, but Oh dear... yet another case of getting confused between archivelog
and cold backups. Of what use is it to you to restore to the time of the
last backup and no further? Surely, the whole point of taking archives in
the first place was (we hope) to permit *complete* recovery to the time of
the failure? For that you need to apply archives...
> The oracle Backup and Recovery Guide recommends that during a cold
> backup restore, the online redo logs are not to be restored (p. 3-10).
> However, if I restore them, the database starts up without any errors.
...and that's precisely why Oracle recommends not to restore the online
logs. If you restore *everything* from the time of the last backup, it's a
beautifully consistent database image that requires no recovery
whatsoever -as you have found. The idea of not restoring the online redo
logs is to force Oracle into seeing the database as all over the place, and
thus require recovery -at which point, you get a chance to play the archive
logs to the database, and roll forward from the point of your backup.
>
> Q2: Does restoring the online redo logs have any adverse effects?
>
Yes. It means you lose data.
> Q3: Do I need to clear out the archived redo log directory prior to
> doing this cold backup restore?
>
Crikey. We really are having some basic problems here, no? Archives are
there to enable your backup to be rolled forward in time. Clear them out
and you can't do that, can you? Clear them out at just precisely the time
you want to use them, and something is seriously amiss (and I suspect it's
your understanding of backup and recovery procedures).
> Q4: After a cold backup restore, is it necessary to start the database
> with RESETLOGS?
>
No. Not unless your redo logs are missing. You want to restore yours, so
it would seem. Therefore, a resetlogs would not be required. If, however,
you want to recover your data as far as is possible, then yes, one would be
required because you wouldn't have restored them, and they'd be missing.
Do yourself a favour: visit my site, go to the books link, and download the
one about backup and recovery. It's only 70 pages long. Should clear up
some issues for you.
Regards
HJR
> Thanks,
> Alex.
Received on Tue Dec 11 2001 - 19:21:53 CST
