在数据库日志中不断的报以下错误
SMON: about to recover undo segment 1
SMON: mark undo segment 1 as available
SMON: about to recover undo segment 2
SMON: mark undo segment 2 as available
SMON: about to recover undo segment 3
SMON: mark undo segment 3 as available
SMON: about to recover undo segment 4
SMON: mark undo segment 4 as available
SMON: about to recover undo segment 5
SMON: mark undo segment 5 as available
SMON: about to recover undo segment 6
SMON: mark undo segment 6 as available
SMON: about to recover undo segment 7
SMON: mark undo segment 7 as available
SMON: about to recover undo segment 8
SMON: mark undo segment 8 as available
SMON: about to recover undo segment 9
SMON: mark undo segment 9 as available
SMON: about to recover undo segment 10
SMON: mark undo segment 10 as available
查询metalink（Note:266159.1）：
[color=gray]Cause
These errors do not indicate rollback segment corruption.

Oracle 8i:
These messages indicate that there is a problem with the "rollback_segments" parameter in the init.ora.

Oracle 9i:
Automatic Undo management is being used. 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.
In case we require any of the offline undo segments for the instance recovery, these messages will appear in alert log.

This is not a bug, this is the intended behavior.
When SMON finds such offline undo segments with transactions needing recovery ,then it does what is intended to do , ie: perform. the transaction recovery in batches of 100 undo records.

看来并不是undo segment损坏块的问题。用metalink上的方法处理，告警不再出现。
[color=gray]Solution

Oracle 8i:
Check that the rollback segment is included in the "rollback_segments" parameter then adding the rollback segment to the parameter. If not, adding the rollback segment and restarting the database will clear up the problem.

Oracle 9i:
Solution 1:
---------------
To stop this messages from appearing you can do the following workaround :

sql> alter session set "_smu_debug_mode"=4;
sql> alter rollback segment "_SYSSMU11$" online;

Where 11 is the number that is appearing in the messages in the alert log.

Solution 2:
---------------
This is fixed in 10g. With the new feature "Fast Ramp-Up" AUM enhancement.