Re: backup UNDO Tablespace (dba_undo_extents)

From: Michael Fontana <>
Date: Tue, 15 Dec 2009 11:15:53 -0600 (CST)
Message-ID: <>

Oracle uses an algorithm to age out used blocks in the undo. Even though they are not in use at any given point in time, they must be cleaned out by an Oracle process and I know of nothing that can be done directly to resize or release them.

Ian is right that they are REQUIRED for database recovery and should be backed up regularly. Using compression in your backup script if you're using RMAN should result in significant savings IF the undo is marked as unused based upon the algoritm. I've seen 80-90% compression rates for undo datafiles. Your mileage may vary...

Michael Fontana

Sr. Technical Consultant

Enkitec M: 214.912.3709



Received on Tue Dec 15 2009 - 11:15:53 CST

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