Re: Max Extents

From: Frank van Bortel <f.van.bortel_at_vnl.nl>
Date: Wed, 03 Nov 1999 10:51:17 -0800
Message-ID: <38208425.6CDD4594@vnl.nl>

stuart.crawford_at_home.com wrote:

> Can you guys tell me how we determine optimum size for extents on a DB.
> The problem we are experiencing has to be handled in some manner so
> that we have an application that we have resize the extents everyday.
> Correct me if I'm wrong but this can't be the only application on an
> Oracle Server that's writes a large number new records into the
> database everyday. How do these applications handle the problem? is it
> a matter of our estimates being way off?
>
> --
> Stuart R. Crawford, MCP, CNA
> Calgary, Alberta, Canada
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.

Why do you need to resize extents? The mere existance of extents does not impact performance (according to Oracle doc). I tend to agree up to a point

where the number of extents reaches very high values (over 4000 or about that).
Estimating extents is always difficult. There's a presentaion by Oracle given
on an OUG conference, stating you need about 3 extent sizes: 160kB, 4M and 160M.
The bottom line here is that you do not want too many different sizes of extents.
Personally, I create tablespaces with a small initial extent (2 blocks) and a
larger next; small reference tables will go into the initial one, larger ones
will not have many extents, as extent allocation (not the existance!) is heavy on resources, and thus performance degrading.

--
Met vriendelijke groet/kind regards,

Frank van Bortel
Technical consultant Oracle

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053-4341500 Received on Wed Nov 03 1999 - 12:51:17 CST