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Re: Algorithm for calculating extent size in LMT

From: Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk>
Date: Tue, 5 Mar 2002 10:29:01 -0000
Message-ID: <1015324060.24905.1.nnrp-14.9e984b29@news.demon.co.uk>

You haven't gone into Oracle 9 with
Automatic Segment Space (ASS) management have you ? This might have some impact on rollback relating to updates to bitmap blocks, as the BMB allocation can be painful when extent sizes are small.

--
Jonathan Lewis
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Dusan Bolek wrote in message
<1e8276d6.0203050041.2d41dc24_at_posting.google.com>...

>nsouto_at_optushome.com.au.nospam (Nuno Souto) wrote in message
news:<3c83682d.4195649_at_news-vip.optusnet.com.au>...
>
>> I won't buy into the "no more problems with LMTs" concept, Howard.
>> I'm currently running them in a production system with 8.1.7/NT.
>> There are indeed problems. Things slow down dramatically once you go
>> over a certain boundary in terms of number of extents. Would love to
>> have the numbers for you at the drop of a hat, but I don't.
>>
>> First noticed the problem with a recursive PL/SQL update that ate up
>> the RLB. All the rollback segment traffic became horrendously slow as
>> the number of extents used went ballistic. Wasn't full, but there
>> were a lot of 16K extents(block size is 8K). I mean a LOT. Boom,
>> performance of the system went out the window.
>
>Yes, just now I'm chasing something similar. I have two tablespaces,
>both with uniform extent size, one has 64kb and the second one has 2MB
>extent size.
>Inserting 500.000 rows (about 20MB) in first one takes about 3
>minutes, second one takes 2 minutes. Still nothing important. However
>delete of those rows takes three minutes on 2MB extent size tablespace
>(and needs 30MB of RBS size), but with 64kb after five minutes
>everything has crashed because of ORA-01628 when RBS hits max extents
>boundary. At that time that RBS has about 125 MB.
>I will try some other tests. I wanna see how much RBS it takes and
>know how much extents is a "critical" number.
>
>--
>_________________________________________
>
>Dusan Bolek, Ing.
>Oracle team leader
>
>Note: pagesflames_at_usa.net has been cancelled due to changes (maybe we
>can call it an overture to bankruptcy) on that server. I'm still using
>this email to prevent SPAM. Maybe one day I will change it and have a
>proper mail even for news, but right now I can be reached by this
>email.
Received on Tue Mar 05 2002 - 04:29:01 CST

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