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Home -> Community -> Mailing Lists -> Oracle-L -> RE: Common Oracle RDBMS Misconceptions - standby db?
there is a paper out on Metalink called Graceful Switchover and Switchback by Lawrence To (who is my hero <G>) that describes this concept. Revised and valid for 7.3, 8.0 and 8.1
Rachel
>From: Jeremiah Wilton <jwilton_at_speakeasy.net>
>Reply-To: ORACLE-L_at_fatcity.com
>To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
>Subject: RE: Common Oracle RDBMS Misconceptions - standby db?
>Date: Tue, 26 Jun 2001 15:21:00 -0800
>
>With graceful standby failover (I demo'd it last year at OOW), you can
>switch
>back and forth, back and forth as many times as you want without recopying
>any
>database.
>
>Basically, when you fail over to a standby, you shut down the primary,
>apply all
>the archived redologs to the standby, then copy all the online logs and the
>controlfile from the primary to the standby. People who use incremental
>checkpoints (DB_BLOCK_MAX_DIRTY_TARGET) must do a 'create controlfile reuse
>database <blah> noresetlogs' at this point. Other people don't have to.
>
>Finally, you "recover database" to get the last one or two online logs and
>open
>the standby "noresetogs." The standby just picks up the chain of SCNs
>where the
>primary left off.
>
>The old primary can be immediately pressed into service as a standby. Just
>generate a standby controlfile on the new primary, copy it into place on
>the old
>primary and start it up as a standby database.
>
>You can go back and forth in this way as many times as you want, and one
>just
>picks up the chain of SCNs where the last one left off. You never get a
>divergence of changes.
>
>I have talked to people who found this out, and looked like they were going
>to
>cry, thinking of the countless hours they had spent after every standby
>failover, recopying to the standby to get it rollong forward again.
>
>In 9i, they have an "automated" graceful failover mechanism for standby
>database. I haven't taken a look at it yet. Probably it is a massive
>java-based GUI that instantly consumes 512Mb or RAM.
>
>--
>Jeremiah Wilton
>http://www.speakeasy.net/~jwilton
>
>On Tue, 26 Jun 2001, Koivu, Lisa wrote:
>
> > OK. I admit my knowledge on standby is minimal, having only read up on
>it,
> > fiddled with it and used the idea sparingly for migrations.
> >
> > However, Jeremiah, I'm very curious. You state that 'Must reinstantiate
> > standby after failover by recopying' is a misconception. Yes, like many
>of
> > the things you state below, the documentation does say that - once you
>open
> > a standby db in r/w mode, it is no longer a valid standby after
>switching
> > back to the primary.
> >
> > Can someone shed some light on why this is not true? It seemed to make
> > complete sense to me. I can see how opening a database read only will
>work
> > and not invalidate the standby, but r/w?
>
>--
>Please see the official ORACLE-L FAQ: http://www.orafaq.com
>--
>Author: Jeremiah Wilton
> INET: jwilton_at_speakeasy.net
>
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-- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Rachel Carmichael INET: carmichr_at_hotmail.com Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Lists -------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).Received on Tue Jun 26 2001 - 19:27:44 CDT
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