Undo segments status is PARTLY AVAILABLE

Alert log shows:

SMON: about to recover undo segment 309
SMON: mark undo segment 309 as available
SMON: about to recover undo segment 312
SMON: mark undo segment 312 as available
SMON: about to recover undo segment 40


To fix:

Check which segments have status PARTLY AVAIABLE and if you do not have any in-doubt transaction (dba_2pc_pending , v$transaction, etc) them:

alter rollback segment XXXXX online;

Best Regards,
Paulo Portugal