Oracle-L: RE: how to keep statistics up to date for CBO

From: Mercadante, Thomas F <NDATFM_at_labor.state.ny.us>
Date: Thu, 09 Oct 2003 04:59:33 -0800
Message-ID: <F001.005D28D5.20031009045933@fatcity.com>

Bob,

I do the following:

First, alter all tables turning monitoring on: alter table {table name} monitoring;

Monitoring says:
"Specify MONITORING if you want Oracle to collect modification statistics on table. These statistics are estimates of the number of rows affected by DML statements over a particular period of time. They are available for use by the optimizer or for analysis by the user."

Then use the following. It recalculates stats for those tables that have been changed enough to warrant stats. The User_Tab_Modifications table will hold a record if 10% of the table was changed. I've been using this for a while now, and it seems to be working fine. As you can see, I have a database table that I insert a record into so I can see how much work is done. I'm happy with it. And I'm not gathering stats for tables that I don't need to. I run this job daily.

Hope this helps.

PROCEDURE WTWDBA.Wtw_Gather_Statistics IS /*
Procedure Name : Wtw_Gather_Statistics

Author         : Tom Mercadante
                 Mercadante Systems Design
				 June 14, 2001
Purpose        :

This Package will use the System DBMS_STATS package to gather statistics for both tables and indexes.

loc_table_name  USER_TABLES.TABLE_NAME%TYPE;
loc_index_name  USER_INDEXES.INDEX_NAME%TYPE;
tbl_count       NUMBER := 0;
indx_count      NUMBER := 0;

loc_start_time DATE;

CURSOR c1 IS
SELECT ut.table_name FROM USER_TABLES UT, USER_TAB_MODIFICATIONS UTM WHERE UT.TABLE_NAME = UTM.table_name;

CURSOR c2 IS
SELECT index_name FROM USER_INDEXES
WHERE table_name = loc_table_name;

BEGIN loc_start_time := SYSDATE;

Gather statistics on tables

OPEN c1;
LOOP
FETCH c1 INTO loc_table_name;

     EXIT WHEN c1%NOTFOUND;
     dbms_stats.gather_table_stats('WTWDBA',loc_table_name);
     tbl_count := tbl_count + 1;

Gather statistics on indexes OPEN c2; LOOP FETCH c2 INTO loc_index_name; EXIT WHEN c2%NOTFOUND; dbms_stats.gather_index_stats('WTWDBA',loc_index_name); indx_count := indx_count + 1; END LOOP; CLOSE c2;

END LOOP;
CLOSE c1;

insert a record into the job log INSERT INTO WTW_JOB_LOG(JOB_NAME, RUN_DATE, START_TIME, END_TIME, MSG_TXT)

VALUES('Wtw_Gather_Statistics',SYSDATE,loc_start_time,

SYSDATE,INITCAP('SCHEMA Stats Complete') || CHR(10) ||
tbl_count || INITCAP(' TABLES Analyzed ') || CHR(10) ||

                    indx_count || INITCAP(' INDEXES Analyzed'));

COMMIT; END; Tom Mercadante
Oracle Certified Professional

-----Original Message-----
Sent: Wednesday, October 08, 2003 4:54 PM To: Multiple recipients of list ORACLE-L

How does one keep CBO statistics for an applications base tables up to date?

We are about to implement the CBO any must read documents.

Many thanks
bob
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Author: Bob Metelsky
INET: bmetelsky_at_cps92.com

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Author: Mercadante, Thomas F
INET: NDATFM_at_labor.state.ny.us

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