Undo management in Oracle database
Undo management in Oracle database
Suggestions on Undo management
1. Check for the ACTIVE,UNEXPIRED and EXPIRED blocks(segments). Don’t add space to the UNDO
when u receive the alert immediately.
| select status,sum(bytes)/1024/1024 from dba_undo_extents group by status; |
2. Monitor the space for a while (wrt the UNDO_RETENTION), as the first alert would be <5 and
the second one would come for <2, be active after <5 and monitor the the ACTIVE,UNEXPIRED and EXPIRED.
3. If you see the active is less, and it is taking from the Expired / Unexpied ones, put the result of the query in the ticket and close.
4. In a generic scenario, we should not bother abt the alerts, unless you get an Undo failure alert from alert log.
The undo keeps the undo information and keeps on deleting the expired undo segments when it requires space.
Also depending on the retention parameter .
See also