Problem with undo tablespace and snapshot too old

From: Daiminger, Helmut <HELMUT.DAIMINGER_at_wwk.de>
Date: Wed, 15 Oct 2003 08:25:02 -0800
Message-ID: <F001.005D33E5.20031015082502@fatcity.com>

Hi!

We are experiencing a weird problem here...

We have automatic undo management enabled and the undo tablespace is 6 GB in size. undo_retention is set to 30 minutes.

when a certain transaction runs, it fails with ORA-1555 Snapshot too old, although the undo tablespace only uses 700 MB (out of 6 GB possible).

That loos weird to me...

Then our other DBA suggested to cut the size of the buffer cache in half and let the transaction run again. We have done that and it worked flawlessly... WHY??? What is the relation between the buffer cache size und rollback (i.e. undo retention)?

This is 9.2 on HP-UX.

Thanks,
Helmut

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Author: Daiminger, Helmut
  INET: HELMUT.DAIMINGER_at_wwk.de

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