RE: Automanagement of extent sizing

From: DENNIS WILLIAMS <DWILLIAMS_at_LIFETOUCH.COM>
Date: Thu, 13 Sep 2001 13:08:20 -0700
Message-ID: <F001.0038DD71.20010913132217@fatcity.com>

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Cherie - We have been using the autoextend feature for 6 months now and have been really pleased with it. I am now studying the Oracle White Papers on the locally managed and uniform extent philosophy and beginning to follow that scheme. I would recommend studying it carefully. We have had a couple of runaways that ate up a lot of disk, that is the most obvious downside. The upside is obvious in the title of the Oracle white paper "Stop Defragging and Start Living". Here are my procedures so far:

1. Use Oracle's new uniform extent recommendations to eliminate free extent fragmentation. Since all extents are the same size, no fragmentation can occur.
2. Use locally-managed tablespaces per Oracle's recommendation.
3. Set all extents in a tablespace to the same size. There are no unusable small free extents, free space is usable by any segment, and administration is minimized.
4. Use only 3 extent sizes: 128K, 4M, and 128M
5. All segments should have less than 1,024 extents. When a table approaches 1,024 extents, it should be moved to the next larger extent size tablespace.
6. Monitor archive log space.
7. Temporary and rollback tablespaces should be divided into 1,024 extents for optimal performance.
8. Export the table before moving it.
9. Use the Oracle "alter table XXX move" command.
10. Use the Oracle "alter index XXX rebuild" command.

Let me know if you have any more questions, and please share your ideas.

Dennis Williams
DBA
Lifetouch, Inc.
dwilliams_at_lifetouch.com
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Author: DENNIS WILLIAMS
  INET: DWILLIAMS_at_LIFETOUCH.COM

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