Undo Tablespace question

  • From: "Paul Vincent" <Paul.Vincent@xxxxxxxxx>
  • To: <oracle-l@xxxxxxxxxxxxx>
  • Date: Fri, 17 Sep 2004 09:16:15 +0100

Now that we've finally got some 9i databases, I'm quite keen to switch =
from Manual to Automatic Undo Management. It all looks pretty =
straightforward, but I do have a couple of questions that the "How To" =
guides don't really address...

1. If I don't have any requirement for long-term retention of Undo data =
after transactions commit, so that the default retention of 900 seconds =
is quite sufficient, then what multiplier should I use when calculating =
the size of my Undo Tablespace relative to the size of the old RBS =
tablespace? Say I currently have 500Mb RBS tablespace, then should a =
500Mb undo tablespace be adequate, or should I allow double (1Gb) or =

2. What monitoring practices are advisable to check the adequacy of the =
undo tablespace provision? Can anyone point me at any webpages with =
articles about monitoring AUM activity, for instance?

3. Once I've switched from Manual to Auto, does the RBS tablespace then =
become completely superfluous? Can it be dropped? And what of the =
"rollback_segments" initialisation parameter? Do I remove this from the =
parameter file, or is it best left there "just in case"?

Before I go diving in, in cavalier manner, I always like to check for =


Paul Vincent
University of Central England

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