Re: Extent sizes

In article <2p0snc$cil@maicgn.SoftwareEngineering>, ar@mai.de (Achim Reiners) says: > >Are there any experiences or guidelines of configuring the first and >next extent size the best way? I usually make the first extent the size of the table upon initial load, and the next extent 1/4 to 1/8 of the final size. >How big can the performance degradation be if configured in a bad way ? >( access is n times slower ? Which n ) I've heard that one of the in-core structures holds only 8 extents in it, and if you jump around in the table, the engine must reread the root page for the table to get to the other extents. I've never been able to measure a difference. >Is it possible to change these for the system tables as well? These >tables were the first ones exceeding the warning level of 8 extents! > Sure. After the CREATE DATABASE statement, and before any CREATE TABLES, as user informix, do: ALTER TABLE SYSCOLUMNS MODIFY NEXT SIZE 32 ; I wish I'd done that before creating our production databases. Anybody know if it's OK to cluster systables and syscolumns? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~ Jim Burks jburks@promus.com ~ ~ Database Administrator / Systems Engineer ~ ~ The Promus Companies, Inc. Memphis, TN USA ~ ~ http://stargate.promus.com/public/jbb.html ~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~