Re: Do I need backup rollback segement tablespace and temporary table ?

From: Frank van Bortel <f.van.bortel_at_vnl.nl>
Date: Fri, 29 Oct 1999 11:38:45 -0700
Message-ID: <3819E9B5.B22CF3D5@vnl.nl>

Jeremiah Wilton wrote:

> Pete Sharman wrote:
> >
> > Theoretically no, but rebuilding the rollback segment tablespace might be too
> > much of a pain for the gain you get anyway.
>
> The poster stated that a hot backup is the the backup method. It seems
> to me there is no way to have a valid backup of the database withouut
> rollback segments. If a recovery were to be attempted without all the
> rollback segments available, there would be no way to get the database
> open at the end of recovery. Open transactions at the point in time to
> which incomplete recovery has been performed would be unavailable for
> application to the uncomitted data blocks in the datafiles. The
> "emergency" underscore parameters that technically allow a database to
> be forced open in these circumstances leave uncommitted data in the data
> blocks, which is a semantically and technically undesirable situation.
>
> As for temporary tablespaces, if they are really of type TEMPORARY, then
> they contain no permanent segments and therefore can be easily
> re-created after a recovery, so they are not essential elements of a
> backup.
>
> --
> Jeremiah
>
> > Dong Tang wrote:
> > >
> > > I have a 250Gb database which is required to be up 24 by 7. So I have to do
> > > online backup. And this database is extremely volatile. So it have a very
> > > big temporary tablespace and a very big rollback segment tablespace ( I have
> > > a tablepspace contains and only contains all rollback segments except
> > > system rollback segment). It also generates about 5 to 10 Gb archived redo
> > > logs per day, which I have to backup to tape. As our backup device is very
> > > slow, I want to backup as less as possible.
> > >
> > > Here is my question: do I have to backup the temporary table and rollback
> > > segment tablespace?
> > >
> > > Since I back up each tablespace at different time, it seems to me, what is
> > > the rollback segment is useless when we do recover, and same reason to
> > > temporary tablespace?

This would mean the sequence of backup matters as well... rollback should then always be backed up last? But what about committed transactions into the first backed up TS?

I was under the impression, that recovery was done via redo (on and offline redo log files), and rollback was regenerated from that. After a roll forward, the (regenerated!) rollback is applied, after which the db is consistent. So yes, you need a rollback segment (but there's allways the system rollback) but I believe you do not need to backup rollback.

On the other hand, I always thought TS in backup mode were not written to until you proved otherwise... ;-)
--
Met vriendelijke groet/kind regards,

Frank van Bortel
Technical consultant Oracle

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053-4341500 Received on Fri Oct 29 1999 - 13:38:45 CDT