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Don Burleson Blog 









Repair UNDO log corruption

Don Burleson


For additional information on handling corruption, see the BC expert notes on corruption and see MOSC Note 1088018.1 - Handling Oracle Database Corruption Issues.

Also see how to  fix system managed undo segments using the _corrupt_rollback_segments parameter.

In rare cases (usually DBA error) the Oracle UNDO tablespace can become corrupted.  This manifests with this error:

ORA-00376: file xx cannot be read at this time

In cases of UNDO log corruption, you must:

   Change the undo_management parameter from "AUTO" to "MANUAL"
   Create a new UNDO tablespace
   Drop the old UNDO tablespace

Dropping the corrupt UNDO tablespace can be tricky and you may get the message:

   ORA-00376: file string cannot be read at this time

If you are getting an ORA-00600 error on undo, see fix system managed undo segments using the _corrupt_rollback_segments parameter.

To drop a corrupt UNDO tablespace:

1 - Identify the bad segment:

   status = 'NEEDS RECOVERY';

------------------------------ ----------------

2. Bounce the instance with the hidden parameter "_offline_rollback_segments", specifying the bad segment name:


3. Bounce database, nuke the corrupt segment and tablespace:

SQL> drop rollback segment "_SYSSMU22$";
Rollback segment dropped.

SQL > drop tablespace undotbs including contents and datafiles;
Tablespace dropped.




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Note: This Oracle documentation was created as a support and Oracle training reference for use by our DBA performance tuning consulting professionals.  Feel free to ask questions on our Oracle forum.

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