Re: Locally Managed Tablespace Uniform Extent

From: Connor McDonald <hamcdc_at_yahoo.co.uk>
Date: Thu, 15 Mar 2001 01:50:20 -0800
Message-ID: <F001.002CD510.20010315004054@fatcity.com>

The advice on Metalink is sound in the sense that using a finite number of extent sizes is a good thing, but (imho) the choice of sizes for extents is largely up to you (a point that the article doesn't really convey).

The key with the uniform extent is avoiding fragmentation issues; combine that with local mgt and the dictionary contention issues pretty much disappear as well. I don't think the actual size of the extents is relevant (once you get well above sizes relative to the max physical read limit).

Thus if you've got 1G segments, just use a 50M or 100M uniform extent sizes in the appropriate tablespaces.

My typical sizes are 256k, 2m, 20m and 200m.

hth
connor

• Jim Walski <jwalski3_at_classicplan.com> wrote: > I have to move a 7.3.4 database to 8i and I want to
  > use the uniform extent
  > size to reduce fragmentation. I read the article
  > "stop defragmenting and
  > start living" and it indicates to have 3 extent
  > sizes - 128K, 4M, 128M.
  >
  > I also read an article on Steve Adams site that
  > indicates to keep the number
  > of extents under (db_block_size/16) - 7 ( which in
  > my case ( 8k block) would
  > be 505 extents. )
  >
  > In the database I am moving there are some segments
  > that are currently 1GB
  > in size, if i was to put those in the 4M tablespace
  > it would already have
  > over 250 extents starting off. Are there any other
  > performance type issues
  > to consider?
  >
  > Should I create another extent size between 4M and
  > the 128M? Maybe 64M
  > increment?
  >
  > Thanks,
  > Jim
  >
  > Jim Walski
  > ClassicPlan
  > Chino, CA 91710
  > email jwalski_at_classicplan.com
  > http://www.classicplan.com
  >
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Connor McDonald
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Received on Thu Mar 15 2001 - 03:50:20 CST