correction: RE: hanging shutdowns, excellent case for a standby recovery database and associated frozen rename target
- From: "Mark W. Farnham" <mwf@xxxxxxxx>
- To: "Robyn" <robyn.sands@xxxxxxxxx>
- Date: Tue, 28 Feb 2006 15:18:32 -0500
You're welcome. Another lister, Brandon Allen, pointed out to me that
shutdown immediate actually waits for rollbacks to complete.
That pending rollbacks would only be an issue if you needed to come down
quickly and resorted to the sequence
shutdown abort; startup restrict; alter system checkpoint; shutdown abort
which is a little better than shutdown abort alone (since in the future
start of the instance the redo application has been done),
but you don't have to wait for the all the rollbacks to complete (which
could be a very very long time).
If you're going to wait for rollbacks to complete as well anyway, my two
cents would be that
shutdown abort;startup restrict; shutdown normal
or
startup force restrict;shutdown normal
should complete as soon as ending with shutdown immediate.
All of this will be moot if you end up using a cleanly stopped copy of
production for such requirements as may be imposed on you for non-technical
motives,
or stop doing cold backups at all.
Regards,
mwf
-----Original Message-----
From: Robyn [mailto:robyn.sands@xxxxxxxxx]
Sent: Tuesday, February 28, 2006 2:01 PM
To: Mark W. Farnham
Cc: Oracle-L@Freelists
Subject: Re: hanging shutdowns, excellent case for a standby recovery
database and associated frozen rename target
Mark,
Thank you for the ideas. We are already having discussions with
Oracle (and EMC) about setting up a complete hot backup site. Perhaps
the points you made below will help us gather the funding required as
the price tag still has mgmt reeling. However, the project has been
given a high priority so there is a very good chance we will pursue it
later this year.
I'm going to do a little more research on the delayed block cleanout
issue so I can present the concepts clearly to the less-technically
oriented. If you have any suggestions on materials, I'd appreciate a
pointer.
Thank you again ... this presents some interesting discussion points.
Robyn
On 2/28/06, Mark W. Farnham <mwf@xxxxxxxx> wrote:
> Robyn:
>
> This seems to me like an excellent case for Alexandrian logic; don't untie
> the knot, hack it apart!
>
> One point I've missed in this thread is ensuring that rollbacks are
complete
> so that neither infinitesmal chances of failure of roll forward nor
rollback
> exist in your cold backup. Since whatever release it was when the ability
to
> open the database before all rollbacks are complete implemented, the side
> effect of pending rollbacks in "cold" backups has from time to time been
> ignored.
>
> Another point is delayed block cleanout.
>
> If what your legal department really wants is a cold backup in the sense
> that all the files can be immutably stamped with a date last modified and
> starting the database does not execute changes to the files, then a mere
> cold backup is in fact not enough.
>
> So make the legal department your ally, who will then provide support for
> you to have a standby-failover site. To create your truly frozen point in
> time immutable database you then would:
>
> 1) Cancel recovery on the standby.
> 2) Copy the standby (locally on the standby site, or to yet another server
> if you want to avoid the rename database step).
> 3) (Optional depending on your choice in step 2.) Rename the copy.
> 4) Recover the COPY of the cancelled recovery standby to an exact known
> point in time.
> 5) Comprehensively query all blocks and do whatever else you have to do to
> trigger all delayed block cleanouts (I think that is version dependent and
> I'm not sure I've seen a comprehensive update on that issue since the last
> time I was somewhat confident I thought I knew how to do that, references
to
> a comprehensive discussion welcome).
> 6) Shut down the cleaned out copy cold.
> 7) Copy the cleaned out copy to whatever backup media your legal
department
> and you can agree on as sufficient.
> 8) Resume remote recovery on the standby. (Actually you can do this after
> step 2 if your choice is a remote machine).
>
> If you have an alternate server, you could also just hot backup to there
and
> do the similar function of starting up and completing recovery, rollback,
> and "cleanout" to produce a very clean cold shutdown.
>
> All this avoids the shutdown on the primary production database altogether
> but still gives you a cold backup which is arguably a superior cold backup
> to the kind that may contain pending rollbacks and delayed block
cleanouts.
>
> Now if I've botched something in this logic, all y'all please be kind, but
> additions/corrections/etc. are certainly most welcome.
>
> Regards,
>
> Mark
>
>
> -----Original Message-----
> From: oracle-l-bounce@xxxxxxxxxxxxx
> [mailto:oracle-l-bounce@xxxxxxxxxxxxx]On Behalf Of Robyn
> Sent: Tuesday, February 28, 2006 9:58 AM
> To: m.haddon@xxxxxxxxxxx
> Cc: Oracle-L@Freelists
> Subject: Re: hanging shutdowns
>
>
> Micheal,
>
> I understand your position and when I arrived here, I made all the
> same arguments. I've been told that our legal department insists on a
> cold backup, and the requirement is non-negotiable. We run full test
> recoveries on all our major systems on a regular basis and we use the
> hot backups to do so. None of us doubt that the hot backups are
> adequate for recovery.
>
> So I guess we're not really 24x7, we're 24x7-15 and that 15 minutes is
> a sacred cow that I need to leave alone right now ...
>
> Thanks for the input and if I was calling the shots, I wouldn't do it
> this way. However, I would still need a script that would shut the
> database down quickly, possibly for maintenance or hardware issues, so
> I really appreciate the suggestions provided on this thread.
>
> Robyn
>
>
>
--
Robyn Anderson Sands
email: Robyn.Sands@xxxxxxxxxx
--
//www.freelists.org/webpage/oracle-l
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