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" <[EMAIL PROTECTED]>
>Reply-To: [EMAIL PROTECTED]
>To: Multiple recipients of list ORACLE-L <[EMAIL PROTECTED]>
>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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