RE: For those using snapshots of Prod Disk Groups - Question
Date: Wed, 10 Jan 2018 17:20:16 +0000
Message-ID: <AM5PR0701MB181000B99C939ABC6F92D2F5E6110_at_AM5PR0701MB1810.eurprd07.prod.outlook.com>
I did a blog post on this subject at http://people.ds.cam.ac.uk/psh35/blog/post/crashconsistentrecovery/. See Oracle support note 604683.1 for information, but so far as I can see it is supported for 12c if you have “crash consistent” snapshots, and know when the snapshot was taken.
We have the entire database on one SAN volume, so it includes the flash recovery area and the online redo logs. I didn’t test whether you can do it without including the flash recovery area. Clearly you should test your approach to see whether it works or not.
We don’t use this approach for production, which for weird reasons is on local storage.
Cheers
PaulH
From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Mark W. Farnham
Sent: 10 January 2018 16:35
To: nenad.noveljic_at_vontobel.com; christopherdtaylor1994_at_gmail.com; 'ORACLE-L' <oracle-l_at_freelists.org>
Subject: RE: For those using snapshots of Prod Disk Groups - Question
If you reload the snapshots containing the online redo logs you will likely be in for an unpleasant surprise.
Online redo logs should only be on a special backup set for complete point in time recovery (if they are backed up at all, which is a discussion of the relative danger of reloading online redo logs when you didn’t mean to versus someone deleting them before they are archived in rotation or backed up by some other means.)
Backing up the current online redo logs (and the control files) to a special media set is a valid first step of recovery that allows you multiple attempts a complete recovery if something goes bump in the night during recovery. This all applies to recovering physical backups unmanaged by RMAN, which has been essentially the same since 6.0.
Find yourself a test host network isolated from your real host and practice this snapshot recovery a few times to be certain of what you have.
The other thing is to make sure the archive log current completes before you do the snapshot archive logs operation.
mwf
From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Noveljic Nenad Sent: Wednesday, January 10, 2018 10:53 AM To: 'christopherdtaylor1994_at_gmail.com'; ORACLE-L Subject: RE: For those using snapshots of Prod Disk Groups - Question
I’m using the following process for snapshoting database in archivelog mode without stopping it:
Alter database begin backup;
Snapshot file systems with data files and online redo logs
Alter database end backup;
alter database backup controlfile to trace as .. ;
alter system archive log current ;
Snapshot file systems with the archivelogs
In the case of rollback:
Stop the database
Rollback all file systems
Recreate controlfile and recover
(Change dbid to avoid conflicts in RMAN)
I also use snapshots for “database cloning” where a new database is created based on the snapshot. The process is similar to rollback except that new file systems are created based on the snapshot and the controlfile backup (as trace) has to be edited to reflect the name of the new database and new file locations.
In case that you’re stopping the source database when doing the snapshot, the FRA is not necessary.
I rely on ZFS instead of storage copy-on-write functionality.
Last but not least, as you correctly mentioned, snapshotting is no replacement for backup/recovery, but is very useful when doing application and database upgrades. It is also invaluable for quick provisioning of development databases.
Best regards,
Nenad
http://nenadnoveljic.com/blog/
From: oracle-l-bounce_at_freelists.org<mailto:oracle-l-bounce_at_freelists.org> [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Chris Taylor
Sent: Mittwoch, 10. Januar 2018 16:21
To: ORACLE-L
Subject: For those using snapshots of Prod Disk Groups - Question
For those of you utilizing storage snapshots of your Prod disk groups, do you also include the FRA contents in your snapshots?
There's an open question we're discussing about whether we need the FRA contents as part of the snapshot.
I'm thinking the FRA contents don't need to be part of the snapshot but I could be mistaken.
Chris
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