Thank you Jeremiah for your explanation. But to clarify, you can't have both databases open at the same time, can you? That's where I hosed stuff up the first time, and I realized why it didn't work immediately after seeing my error (incompatible archive logs). Or am I off track?
-----Original Message-----
From: Jeremiah Wilton [SMTP:[EMAIL PROTECTED]]
Sent: Tuesday, June 26, 2001 7:21 PM
To: Multiple recipients of list ORACLE-L
Subject: RE: Common Oracle RDBMS Misconceptions - standby db?
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?
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