Just to add on to what Kevin said….I used to have conversations w/ my storage guy ,and get totally confused, cause he was speaking EMC language and I was speaking Oracle language.  When we finally got someone from EMC on the phone that understood both sides, the terminology she used, which finally allowed me to see the light, was that one method is “recoverable” the other is “restartable”.  Recoverable refers to a conventional backup.  You put the tablespaces into backup mode, split the mirrors, and exit backup mode.  The “snapshot” is not recoverable, it’s restartable.  It’s basically a copy of everything, datafiles, controlfiles, and redo logs, all self-consistent.  Note that the restartable snapshot MUST include the redo logs, and a recoverable backup copy NEVER should.

Now, granted, up to now, this was about NetApp, and I’m talking EMC, but, conceptually, the ideas are the same.  The key concept to get is that a snapshot, taken while the database is up and running, and tablespaces are not in backup mode, is restartable, not recoverable.  The confusion I referred to in previous conversations w/ my storage admin all centered around the fact that he didn’t make (didn’t know to make) a distinction between restartable and recoverable!  He’d say “EMC says it will work, they have customers that do it all the time!”  And I’d tell him “If the tablespaces aren’t in backup mode, I can’t recover it!!”

-Mark

be aware that a database in a filesystem snaphot looks EXACTLY like it would if you pulled the electricity from the database server when Oracle was up and running. You cannot roll forward from such an image. NetApp documents all this quite well...just be aware that there is no magic ...

From: oracle-l-bounce@freelists.org [mailto:oracle-l-bounce@freelists.org] On Behalf Of Vasu Balla
Sent: Friday, July 20, 2007 10:24 AM
To: vbarac@Alghanim.com; oracle-l@freelists.org
Subject: RE: NetApp flier - based snapshots and db backups

Oracle OnDemand, which hosts more than 1000 databases on netapp filers, uses this snapshot functionality for backup. you are not alone :)

vasu