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Re: Archive log confusion

From: <oratune_at_aol.com>
Date: Wed, 27 Sep 2000 01:13:17 GMT
Message-ID: <8qrhj9$quo$1@nnrp1.deja.com>

In article <8qr8gp$jm4$1_at_nnrp1.deja.com>,   kal121_at_my-deja.com wrote:
> Here's the question:
>
> If the output of "ARCHIVE LOG LIST" is this at 12:00:00 am,
>
> Database log mode ARCHIVELOG
> Automatic archival ENABLED
> Archive destination /oracle/log
> Oldest online log sequence 30
> Next log sequence to archive 31
> Current log sequence number 33
>
> and I start a hot backup at 12:00:01 am, what is the MINIMUM archive
> log sequence number I need to go with this backup?
>
> Books I have read said you need the "Oldest online log sequence", but
> is that really true? It seems to me that you only need the archive log
> sequence that contains the changes that occurred at 12:00:01 (the
 start
> time of your hot backup) and beyond. So, wouldn't that be the "Current
> log sequence number 33"? - since that is the one that is being written
> to at 12:00:01 am, NOT the "Oldest online log sequence 30", which was
> written before 12:00:01. And 33 is the one that will become the
 archive
> log of the online redo log that was being written to at the time of
 the
> hot backup.
>
> I've also read that you only need those archive logs that are older
> than the timestamp of the beginning of your last hot backup. But even
> this doesn't entirely make sense because 31 is the next sequence to be
> archived (the ARCH is slow), so 31 will be older than 12:00:01 by the
> time it is archived, but log 33 is first online redo log being written
> to at the time of the hot backup, not 31. 31 has changes in it that
 are
> older than the start of the hot backup, so that hot backup doesn't
 need
> those changes. It only needs changes in 33, right?
>
> Somebody please clarify.
>
> Thanks
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.
>

Yes, you are correct in that the only changes you will need to restore are those made during the hot backup period. However, why waste time thinking of which log to keep, which log to use, etc.? Follow the documentation and you'll do no wrong since Oracle will decide which logs it needs and apply only those to the tablespaces. An archive log kept and not used is far better than an archive log discarded and then later needed.

--
David Fitzjarrell
Oracle Certified DBA


Sent via Deja.com http://www.deja.com/
Before you buy.
Received on Tue Sep 26 2000 - 20:13:17 CDT

Original text of this message

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