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RE: 9i DataGuard, RAC primary - secondary offline for networkmaintenance

From: Ric Van Dyke <>
Date: Tue, 5 Dec 2006 19:15:45 -0600
Message-ID: <>


You are very correct that as stated in the documentation the version of Oracle are supposed to be the same (as in identical) on the primary and the standby. However I worked with the folks who developed the standby database code and this is more of a CYA requirement then a real one. There was some long discussions about this requirement and I believe that "paranoia" won out, the idea being it's better to be over restrictive then not. The issue is more about the format of the redo log stream then anything else. It's very likely that this setup will work just fine. And given that Tony (apparently) has been running with this setup for some period of time, it's again likely that this will continue to work just fine.  

The escape clause for Oracle should Tony run into bazaar problems will likely be that the versions of Oracle are different in his configuration. However I figure it's very unlikely that this will cause an issue. Currently I agree that if your production system needs a certain patch level then having a standby at a different patch level is at least odd.  

Ric Van Dyke

Hotsos Enterprises

Hotsos Symposium March 4-8, 2007. Be there.

[] On Behalf Of Carel-Jan Engel Sent: Tuesday, December 05, 2006 5:46 PM To:
Cc: oracle-l
Subject: Re: 9i DataGuard, RAC primary - secondary offline for networkmaintenance  

Hi Tony,

See inline
On Tue, 2006-12-05 at 22:09 +0000, Tony Sequeira wrote:  

Hi all,  

I have a 2 node 9i RAC primary (Win 2003), mandated by the application.  

Have a physical standby  

All appears to be going well, teething problems over (touch wood).

Cross your fingers. Oracle DOESN'T support DG environments with different versions. It appears you haven't checked the prerequisites carefully enough.

Your standby database is not, mind that you never did a startup migrate and ran catpatch.sql for on the primary. Since your standby is a physical copy of the primary, this database is as well. I don't know why you keep the standby (probably for High Availability reasons), but switching/failing over to it might pop up some surprises. 'Results are unpredictable' is the right phrase here. I cannot emphasize enough that an HA configuration needs SYMMETRY. You're violating this rule#1 here.    

The primary is running in maximum performance mode.  

The secondary server is due to go down for about 24 hours for absolutely

vital electrical maintenance work.  

I believe that this will be OK, and that the secondary will catch up when brought online again.

Yes, no problem. Not that you can use it, effectively it is unavailable as long as you have this mixed version setup running. I have never investigated the combination of a failover/switchover with startup migrate/run catpatch. It might work. Please test it and share your experiences.
There is one big assumption involved in your theory: You have to keep the archived redo log files long enough for the standby to fetch them after it switched on again, As Ric Van Dyke posted while I am writing this.    

Any think or know different? I'm trying to plan for any glitches now, the primary database is a vital 24/7 system.

If so, either upgrade your primary to or install at the standby. You don't want surprises at the eve of failover with a vital 24x7 system.    

I am aware of Note:259804.1 - particularly the section 'Real Application Clusters and Data Guard Redo Apply During a Network Outage'.

Get aware of erations.htm#52221 , 3rd bullet, too.

Best regards,

Carel-Jan Engel

If you think education is expensive, try ignorance. (Derek Bok) ===  

Received on Tue Dec 05 2006 - 19:15:45 CST

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