Re: Log Switches in RAC
- From: Yong Huang <yong321@xxxxxxxxx>
- To: kaygopal@xxxxxxxxx, Rajesh.Rao@xxxxxxxxxxxx
- Date: Wed, 11 Nov 2009 15:03:42 -0800 (PST)
> If any of the thread is not archived for longer duration
> and if the critical changes are recorded in that thread,
> you may not be able recover the database as the physiological
> logging requires all the changes from ALL the thread to make
> the recovery complete
There is (or was?) the concept "force archive SCN". I know of two sources
where this is talked about. Rama Velpuri's "Oracle(8) Backup and
Recovery Handbook" and Lawrence To's "Archiving Tips and Hints". The
latter can be found at
https://support.oracle.com/cgi-bin/cr/getfile.cgi?p_attid=75071.1:219081
"Threads are kept relatively current by forcing log
switches or kicking idle instances to archive. For an open and enabled
thread, a lock is used to kick an idle instance.
For a closed and enabled thread, the ARCH process for an active instance
will log switch and archive the closed
thread. A force archive SCN is maintained in the control file to implement
this feature.
"OPS: The ARCH process scans the archive link list found in the control
file and archives all inactive redo logs
whose SCN is less than the force archive SCN. Oracle strives to archive
any log that contain less than or equal to the
force archive SCN. Generally, the log with the lowest SCN is archived
first."
Yong Huang
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