RE: how to keep statistics up to date for CBO

Wolfgang Breitling Thu, 09 Oct 2003 07:54:21 -0700

One reason to collect index stats separately would be if you use estimate for the collection of the table statistics. In that case I collect the index stats separately with a compute. Index statistics collection is fast enough to always go for exact statistics rather than sampling.

At 08:44 AM 10/9/2003, you wrote:

Tom,

why would you want to collect table/index stats separately? Any reason? I prefer cascade=>true with mine.

Raj --------------------------------------------------------------------------------
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-----Original Message-----
From: Bob Metelsky [<mailto:[EMAIL PROTECTED]>mailto:[EMAIL PROTECTED]
Sent: Thursday, October 09, 2003 9:49 AM
To: Multiple recipients of list ORACLE-L
Subject: RE: how to keep statistics up to date for CBO
Thank you very much Tom. That gives me an excellent starting point. I'll
begin to implement this in a devel environment and get a feel for it.
Thanks again!
bob
-----Original Message-----
Sent: Thursday, October 09, 2003 9:00 AM
To: Multiple recipients of list ORACLE-L
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 -- Please see the official ORACLE-L FAQ: <http://www.orafaq.net>http://www.orafaq.net -- Author: Bob Metelsky INET: [EMAIL PROTECTED]

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Wolfgang Breitling Oracle7, 8, 8i, 9i OCP DBA Centrex Consulting Corporation http://www.centrexcc.com


--
Please see the official ORACLE-L FAQ: http://www.orafaq.net
--
Author: Wolfgang Breitling
 INET: [EMAIL PROTECTED]

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RE: how to keep statistics up to date for CBO

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