Re: Pmon & SMOn

From: Mark D Powell <Mark.Powell_at_eds.com>
Date: 14 Nov 2005 05:39:24 -0800
Message-ID: <1131975564.087516.156720@g43g2000cwa.googlegroups.com>

If a user session abnormally terminates by hitting an unhandled Oracle error then pmon control the rollback of the current transaction. Pmon usually uses the user session to perform the actual rollback.

If the instance crashes the as part of crash recovery smon performs transaction rollback. Current versions of Oracle do not have to complete all transaction rollbacks prior to letting user sessions on the system. If a user session attemps to access data held by an incomplete transaction then that session performs the rollback.

The following two short articles on looking at the rollback segments might be of interest to you.

Is there a way to detect processes that are rolling back, and can I figure out how long it will take ?
http://www.jlcomp.demon.co.uk/faq/rolling_back.html

How do I associate an active session with a rollback segment ? http://www.jlcomp.demon.co.uk/faq/active_rollback.html

HTH -- Mark D Powell -- Received on Mon Nov 14 2005 - 07:39:24 CST