Re: Algorithm for calculating extent size in LMT

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.

--
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Dusan Bolek, Ing.
Oracle team leader

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