Re: MTS&Cost based Optimzer

If you have the time and horsepower, analyze the database. If not, wait until somebody complains and run a trace/tkprof against their SQL. You may want to consider using histograms on selected tables. There was a discussion on using histograms earlier this month. Steve Adams wrote a script to help in identifying possible candidates for histogram creation. It's on his web site at:

        http://www.ixora.com.au/scripts/query_opt.htm#consider_histogram

Be judicious with its use.

In general, I've found it useful to consider running an analysis of large tables used frequently in the select and where clauses of SQL statements.

Regards,

David A. Barbour
Oracle DBA

Deepender Kr Gupta wrote:
>
> How would you decide that out of total big and small tables (say 1500) these
> are the tables need to be analysed and these are not, as in our case
> Transaction types are both OLTP and DSS ??
>
> -----Original Message-----
> Carmichael
> Sent: Tuesday, April 24, 2001 6:46 PM
> To: Multiple recipients of list ORACLE-L
>
> turning on cost-based is easy: set the optimizer_mode parameter to choose
> in your init.ora, stop and start your database and then analyze all your
> tables.
>
> HOWEVER (and this is a biggie) this will not automatically make all your
> queries run faster. You will need to examine each and every query to see if
> it needs to be rewritten to take advantage of CBO. In fact, sometimes there
> are queries that run faster in rule-based, and I have had to include hints
> in queries to force the optimizer to run rule.
>
> >From: Venkat_Kalepalli <Venkat_Kalepalli_at_satyam.com>
> >Reply-To: ORACLE-L_at_fatcity.com
> >To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
> >Subject: MTS&Cost based Optimzer
> >Date: Tue, 24 Apr 2001 02:25:25 -0800
> >
> > > Hello folks!
> > >
> > > I am working in SUN solaris 5.6 with Oracle 8i. I want to implement MTS
> > > on the Oracle server. Next we are running with Rule based optimizer and
> > > we want to change to costbased optimizer.
> > >
> > > I want to know what are the advantages we get on this and what are the
> > > steps to implement this?
> > >
> > > Any help is grateful...
> > >
> > > Rgd
> > > Venkat
> > > DBA.
> > >
> > >
> > >
>
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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.com
-- 
Author: David A. Barbour
  INET: dbarbour_at_nucentrix.net

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