RE: standbys and unrecoverable operations

Josh,  

I'm not a standby or DataGuard expert, but, think about what the unrecoverable change # represents. It's the SCN at which the last unrecoverable operation occurred on that datafile. So, if the primary is ahead of the standby, that means there are operations which have occurred on the primary which did not propogate to the standby. This is a corruption waiting to happen. If you activate the standby and a datablock is accessed that was loaded unrecoverable on the primary, you'll encounter an ORA-26040.  

So, I assume (don't have a standby setup handy to confirm it) that the default safe position is that they are equal, since, when you clone from the primary to initially create the standby, they'd (presumably) be equal. At that point, the only way for them to get out of sync is if you do an unrecoverable (aka nologging) load in the primary database.  

Corrections welcome from those with actual DG and standby experience! ;-)  

Hope that helps,  

-Mark
 

PS Note that in 9i (can't remember if it was 9.0.1 or 9.2.0 intorduction) you can do ALTER DATABASE FORCE_LOGGING=TRUE; and everything will log, even if people try to do nologging loads.

From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Josh Collier Sent: Tuesday, November 15, 2005 4:52 PM To: oracle-l_at_freelists.org
Subject: standbys and unrecoverable operations

Greetings,  

The Oracle documentation says that if the unrecoverable_change# for a datafile reported (v$datafile) by the primary is greater than that reported by the standby then you will need to recover that datafile (by copying it over from the primary) in order to avoid block corruption errors if the standby is activated.  

Does this also hold if the unrecoverable_change# are identical?  

have a good day,  

Josh C.

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http://www.freelists.org/webpage/oracle-l Received on Tue Nov 15 2005 - 16:02:17 CST