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Re: Locally Managed Tablespaces - Questions.

From: Jonathan Lewis <>
Date: Tue, 15 Apr 2003 22:34:04 -0800
Message-ID: <>


I think there's a lot of information (and mis-information) on the market about
the 'best' thing to do, but so many systems are so far from optimal that often it doesn't make any difference if you make some change from 'vaguely adequate' to 'perfect'. I think the 'number/size' for extents falls into this category as far as performance is concerned.

As far as the extent map block argument is concerned - you only have to consider the side-effect of ASSM, and the need to read L1 blocks to complete an FTS, and you realise that Oracle Corp. thinks a few spare single block reads are pretty irrelevant.

The argument I have for having a few tablespaces with the 'relevant' extent size is the baby-sitting argument. If I'm going to have a report telling me about growing objects, I'd like to get one or two lines each week. Not a one-hundred line report each week where I have to add some intelligence at read-time to decide if any of the lines mean anything.


Jonathan Lewis

  The educated person is not the person   who can answer the questions, but the   person who can question the answers -- T. Schick Jr

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The Co-operative Oracle Users' FAQ

> Whilst I agree with Steve's assessment as it applies
> to squeezing the n'th degree of efficiency from
> Oracle, I'd be keen on hearing from anyone that
> suffered any detectable / noticeable performance
> degradation from having an excess of extent map blocks
> in their system.
> Don't get me wrong, I've no doubt that such a
> degradation must exist, but I'd be very surprised if
> there are many databases out there that are that well
> optimized so that this becomes a relevant issue.
> If that's the case, then I'm back to my argument that
> for almost all databases, you can quite happily get
> away with a 1m extent size for *every* segment in the
> database (assuming a 4G ceiling on segment size)
> Cheers
> Connor

Please see the official ORACLE-L FAQ:
Author: Jonathan Lewis

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Received on Wed Apr 16 2003 - 01:34:04 CDT

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