unrecoverable_change is from v$datafile, which is from controlfile,
not from datafile header.
if you refresh controlfile at standby, this all the information at
standby v$datafile is incorrect.
It is very hard to detect. in a complex production environment.
enable force_logging in 9i is a good idea for standby
On 11/16/05, Bobak, Mark <Mark.Bobak@(protected):
> 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,
> 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@(protected)]
> On Behalf Of Josh Collier
> Sent: Tuesday, November 15, 2005 4:52 PM
> To: oracle-l@(protected)
> Subject: standbys and unrecoverable operations
> 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.