Re: Online backup: Backup online redologs?

From: Charles Fisher <Charles.Fisher_at_alcoa.com>
Date: Fri, 18 May 2001 17:17:10 GMT
Message-ID: <Pine.GSO.4.31.0105181156360.987-100000@unknown>

On Fri, 18 May 2001, Howard J. Rogers wrote:

> > In a related question, can the dbverify command be used to check the
> > consistency of a hot backup of a redolog?

> No, because it is only designed to be applied to datafiles (online, or
> offline, or part of a datafile whether on or offline). The fact that there
> is a 'blocksize' parameter should alert you to this: there is no such thing
> as an Oracle block with the redo logs (as also attested by the fact that
> log_checkpoint_interval is measured in *O/S* blocks, not Oracle blocks).
> I'm actually slightly gobsmacked that it worked at all, and full marks for
> perservereing (or however it's spelled) to find a block size that appears to
> do the trick -but the results will nevertheless be utterly meaningless, and
> I wouldn't waste your time further.

Actually, dbv suggested a blocksize of 1024 when I tried to run it. Pardon me for running the dbv from Oracle 7; Oracle 8 dbv generates slightly different messages but the summaries are the same. I guess that you yourself would see this if you hot-copied your redo and ran dbv on it.

Well, assuming that dbverify won't work, and that I do want hot backups of the redologs for controlfile rebuilds, what do you think about this method:

alter system archive log current, to start a new redolog and minimize the risk of an unplanned log switch,
hot copy the redolog datafiles with os tools, and rename them to something like 'dont-use-redo1.log',
alter system archive log current again, so the corrupt log that I just copied now has an intact archive log.

Since dbverify won't work, there is no way to tell if I will "get away" with this without a full restore, which does not make me happy.

Is this the cleanest way to do this dirty thing?

Charles J. Fisher - Consultant
Alcoa Davenport Works
(319) 459-2512 Received on Fri May 18 2001 - 12:17:10 CDT