RE: oracle docs do say # of extents effect performance

From: Nelson, Allan <anelson_at_midf.com>
Date: Fri, 20 Jun 2003 09:11:10 -0700
Message-ID: <F001.005B6464.20030620085504@fatcity.com>

It is the old argument that was made to justify one or only a few extents. Empirically the idea does not hold up. This idea is now classified as a myth but the Oracle docs have not caught up yet.

Allan

-----Original Message-----
Sent: Friday, June 20, 2003 11:20 AM
To: Multiple recipients of list ORACLE-L

I just read a .pdf by a couple of people at oracle called Stop Fragmenting and start living where it says not worry about the number of extents in a tablespace. However in the administrators doc it says the following:

Estimate Table Size and Set Storage Parameters Estimating the sizes of tables before creating them is useful for the following reasons:

You can use the combined estimated size of tables, along with estimates for indexes, rollback segments, and redo log files, to determine the amount of disk space that is required to hold an intended database. From these estimates, you can make correct hardware purchases and other decisions.

You can use the estimated size of an individual table to better manage the disk space that the table will use. When a table is created, you can set appropriate storage parameters and improve I/O performance of applications that use the table. For example, assume that you estimate the maximum size of a table before creating it. If you then set the storage parameters when you create the table, fewer extents will be allocated for the table's data segment, and all of the table's data will be stored in a relatively contiguous section of disk space. This decreases the time necessary for disk I/O operations involving this table.

this is at the following link:

http://download-west.oracle.com/docs/cd/A87860_01/doc/server.817/a76956/ tables.htm#208

am I reading this wrong or is Oracle stating that you should have less extents in a table? I know several people on here have posted that the number of extents used by an object is almost irrelevant.

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Author: Nelson, Allan
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