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Of course, I should point out that
-- Jonathan Lewis http://www.jlcomp.demon.co.uk Next Seminars UK July / Sept Australia July / August Malaysia September USA (MI) November http://www.jlcomp.demon.co.uk/seminar.html Jonathan Lewis wrote in message ...Received on Wed Jul 03 2002 - 04:10:02 CDT
>
>It is definitely possible that I could have said that,
>but it was a typing error if I did. From a clean install
>there is one bitmap per file.
>
>With an 8K block size, the typical header will be
>64K, of which 2 blocks are not bitmap, so you get
>48K of bits, or 384,000 bits - so the limit is high,
>but not extreme.
>
>So if you do have lots of objects which are all
>rapidly extending because they all have a
>(relatively) small you have at least three overheads
>to consider:
> a) scanning the bitmap for a free bit
> b) the contention from multiple processes
> wanting to update the same bitmap
> c) the redo generated by the bitmap update
>
>These are probably likely to be pretty insignificant.
>
>Updates to TSQ$ if you have quotas imposed, will
>probably be a more important concern.
>
>The fact that a segment header at 8K only maps
>505 extents may have some performance side effect.
>
>
>But to me, one of the most important issues is the
>administrative one. If you want an email sent to you
>whenever an object grows - just in case of a space
>threat - you need the right sized extent because
>the "right" email is the one that:
> a) doesn't appear very often
> b) has just a couple of lines when it appears
> c) is full of nothing but important content.
>
>If you get a report every day that say 75 objects
>have all extended by somewhere between 5 and 50
>extents, you stop seeing what's in front of you.
>
>
>
>--
>Jonathan Lewis
>http://www.jlcomp.demon.co.uk
>
>Next Seminars
> UK July / Sept
> Australia July / August
> Malaysia September
> USA (MI) November
>http://www.jlcomp.demon.co.uk/seminar.html
>
>Niall Litchfield wrote in message
><3d22b879$0$230$ed9e5944_at_reading.news.pipex.net>...
>>
>>Jonathan pointed out earlier (if I read him correctly) that there is a
'per
>>tablespace' limit for the number of extents which will fit in the bitmap.
>So
>>you may not get degradation on any individual table with a few thousand
>>extents but if the bitmap is dealing with hundreds of thousands of extents
>>it may suffer.
>>
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>
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