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UNDO_RETENTION what is the largest value recommended?

Beauty_and_dBestJan 24 2018 — edited Jan 25 2018

Db = 10.2.0.5

OL5

Hi ALL.

We have been experiecing ORA-01555 when purging data in a large history table.

And this weekend, we will run again a large purge program which can not be done by chunks.

Please help how to monitor.

Cause: request failed due to ORA-01555: snapshot too old: rollback segment number 16 with name "_SYSSMU16_1232623801$" too small

Our UNDO tablespace is set to autoextend on, so space is not a probem.

Can I say that the problem is our UNDO_RETENTION parameter? How long can I set its value to? Can I set it to 48 hrs?

SQL> show parameter undo

NAME                                 TYPE        VALUE

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

undo_management                      string      AUTO

undo_retention                       integer     2000  << is this value in seconds?

undo_tablespace                      string      APPS_UNDOTS1

Can you share me script how to monitor if ORA-01555 is about to happen?

Do I need to create a new UNDO tablespace so that I can assign the PURGE program to it?

Please help...

Kind regards,

jc

This post has been answered by Joerg.Sobottka on Jan 24 2018
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