Re: about analyse table..

From: Rachel Carmichael <carmichr_at_hotmail.com>
Date: Fri, 23 Mar 2001 07:43:59 -0800
Message-ID: <F001.002D5E22.20010323053521@fatcity.com>

if you have your database in the "CHOOSE" mode for the optimizer (using the cost-based optimizer) and you don't analyze your tables, Oracle doesn't have good information to determine the query path.

If you do "analyze table <tablename> compute statistics" the entire table is read to gather the statistics

if you do "analyze table <tablename> estimate statistics" (and you can give it the percentage to estimate on) then Oracle takes a sampling of the data to generate the statistics

analyze table will also cause all indexes to be analyzed, although you can analyze the indexes separately.

If you do analyze the tables in your database, make sure to analyze all of them as a query with even one table not analyzed will have performance degradation.

For more details, you can start with the SQL Reference manual and look up the ANALYZE command

>From: "Saurabh Sharma" <saurabhs_at_fcsltd.com>
>Reply-To: ORACLE-L_at_fatcity.com
>To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
>Subject: about analyse table..
>Date: Thu, 22 Mar 2001 22:00:23 -0800
>
>hello,
>
>i'm not very familiar with the analyse table command. and not fully aware
>of it's advantage or limits to analyse the tables.
>could anyone pls help me with this cmd, how to see the analysed statistics,
>etc.
>any help is highly appreciated.
>
>thanks in advance.
>
>saurabh sharma

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Author: Rachel Carmichael
  INET: carmichr_at_hotmail.com

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Received on Fri Mar 23 2001 - 09:43:59 CST