How could I find the SQL statement who get this message ?

Question

ORA-01555 caused by SQL statement below (Query Duration=11191 sec, SCN: 0x0854.723b9c32)
... How could I find the SQL statement who got this message ?
Thanks, Paul

Answer 1

ORA-01555 means that the UNDO/ROLLBACK space is not large enough.
This occurs because the SELECT statement is attempting to read the UNDO, but the UNDO has been released (transactions have committed or rolled back) and reused.
The following are SOME of the reasons I have seen this to occur:
1) Updates in a loop, with commits happening in the same loop
- this will mark the UNDO available quickly and quickly reuse it. Then when the SELECT wants to rebuild a block, the UNDO used to rebuild the block has been reused (solution, make the UNDO bigger)
2) A SELECT cursor used to control a loop in which updates are performed, and a 'done' flag is marked against the current cursor record, and commits are performed at the end of each loop, prior to fetching the next record
- same problem as above, but it hits the current process. Same solution
3) A 'month end' activity spike occurs, and all sorts of transactions create updates. There is a report that reports the activity - amusingly it needs to start at the beginning of all the work and updates periodically by doing a huge SELECT up front. This is then used to drive a loop which attempts to get information from the various transactions that have been updated and committed. After a while, the SELECT gets an ORA-01555
- same problem as above and same solution. Get a bigger UNDO segment.
You say this only happens once a month. That should give a hint.
I wouldn't bother with which SELECT statement, as much as which APPLICATIONs are being run when it happens.
One way around this - use 10g and set the guaranteed retention period. All sorts of other things will break, by no more 1555. <g>