Only thing I'd add I like to compute exact stats for
any table less than 'n' rows (where 'n' is small and
you can insert your own value here).
Nothing to do with the performance of the stats
collection itself, more the access plans that
subsequently result. If the optimizer thinks a table
has 100 million rows instead of 90 million, then its
unlikely to dramatically affect the outcome of the
access path evaluation, so small sampling when doing
the stats should be fine. But the optimizer thinks a
200 row table only has 100 rows, then you can end up
with lots of grief (especially in nested loop
scenarios) so a compute may well be the best option
hth
connor
- Wolfgang Breitling <breitliw_at_centrexcc.com>
wrote: > 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
>
>--------------------------------------------------------------------------------
>
> >
> >Rajendra dot Jamadagni at nospamespn dot com
> >All Views expressed in this email are strictly
> personal.
> >QOTD: Any clod can have facts, having an opinion is
> an art !
> >
> >-----Original Message-----
> >From: Bob Metelsky
>
[<mailto:bmetelsky_at_cps92.com>mailto:bmetelsky_at_cps92.com]
> >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: bmetelsky_at_cps92.com
> >
> >Fat City Network Services -- 858-538-5051
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> >San Diego, California -- Mailing list and
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>
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> >also send the HELP command for other information
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> >Please see the official ORACLE-L FAQ:
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>
>**************************************************************************************
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> for the named
> >recipient(s) above and may contain information that
> is privileged,
> >attorney work product or exempt from disclosure
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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: breitliw_at_centrexcc.com
>
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Connor McDonald
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Received on Thu Oct 09 2003 - 20:04:24 CDT
