Re: Undo Tablespace question
- From: Paul Drake <bdbafh@xxxxxxxxx>
- To: paul.vincent@xxxxxxxxx
- Date: Fri, 17 Sep 2004 16:41:30 -0400
2 things:
1. what patchset are you on? (gratuitous plug for Alert #68 patchsets,
e.g. 9.2.0.5.3)
2. data loads - you may find that a lrage number of undo segments are
brought online - and not released in the amount of time that you would
expect, even with undo_retention set to 300 seconds.
Check for posts by Dan Fink and Kirti Deshpande covering such issues.
I believe that they both have papers up on the RMOUG site.
hth.
Paul
On Fri, 17 Sep 2004 09:16:15 +0100, Paul Vincent <paul.vincent@xxxxxxxxx> wrote:
> 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 =
> more?
>
> 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 =
> "gotchas"!
>
> Regards,
>
> Paul Vincent
> DBA
> University of Central England
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