Re: Any performance issues for hot backups ??

Bas Ven wrote:
>
> I am looking into the possibilities Oracle can give me
> to do 'hot backups'. From a developers point of view I don't
> have to do anything, except require that the database is started
> in the ARCHIVELOG mode. (at least that is what I read so far,
> if I am wrong in this assumption, please let me know).
>
> I am pretty sure that when I write the above as a conclusion
> I will immediately be getting responses (from within my company)
> saying that this solution is not workable because of performance issues.
> Therefor I am asking this group for 'field' experiences. Are there
> any reports or does anyone have experience that indicates that the
> performance of the Oracle database degrades (significantly) or
> hardly affects it when running in archivelog mode ?
>
> Regards,
>
> Bas
> --
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> J.B. Ven | Alcatel Telecom Nederland
> Phone: +31 (70) 3079130 | P.O. Box 3292
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Bas Ven,
I recently completed some scripts to perform hot backups and my users did not even know it happened, until I told them. There is a marginal performance hit when running in archive log mode, but the recovery benefits out weigh the performance cost.

Someone else answered your post saying Oracle uses an OS copy to archive filled redo logs, but I don't think that is correct. I noticed it took longer for Oracle to archive a redo log then it took me to copy an identical file using an OS copy. I beleive Oracle will read from each redo log (ie. all mirror copies) to make sure none of the online redo logs are corrupt, and this causes it to take longer. I have the luxury of a dedicated disk to hold archived redo logs and use a script to compress the archived logs (getting approx. 5:1 compression) and another script to page/email me if the file system reaches 90% capacity and then remove redo logs older then 1 day (since they are already backed up on tape).
Also, the v$log_history can tell you how ofter log switches occur, so you can estimate how much archive space you need.

FYI, I'm using Oracle 7.3.2.2 on Solaris 2.5.1

Eric Fall
Automatic Data Processing
emf_at_aa.csg.com Received on Fri Jun 06 1997 - 00:00:00 CDT