SMON ABOUT TO RECOVER UNDO SEGMENT s messages in alert log

Question

Problem
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There are lots of messages appearing in alert log of the following form:
SMON: about to recover undo segment %s
SMON: mark undo segment %s as available
Reason
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When the recovery is going on after a abnormal shutdown. Cause These errors do not indicate rollback segment corruption. In oracle8i, this may becoz of problem with the "rollback_segments" parameter in the init.ora. where as in oracle9i, When the instance is shutdown, during the next startup instance recovery needs to take place.
In AUM we do not have any control over which undo segments will brought online after the instance startup.When SMON finds such offline undo segments with transactions needing recovery ,then it does what is intended to do recovery.
Solution
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with oracle8i, we need to cross check rollback_segments" parameter in the init.ora
with oracle9i,
first note down segment from SMON: mark undo segment %s as available
sqlplus "/ as sysdba"
alter session set "_smu_debug_mode"=4;
alter rollback segment <offline segment name> online;
e.g. alter rollback segment "_SYSSMU11$" online;
Where 11 is the number that is appearing in the messages in the alert log.

Answer 1

What's the point duplicate metalink doc here,
SMON: ABOUT TO RECOVER UNDO SEGMENT %s messages in alert log
Doc ID: Note:266159.1
besides it's violation of Oracle support service contract.