Re: Huge optimization costs with 9.2

We has problems with another undocumented parameter that changed when we migrated to 9i in August last year. _B_TREE_BITMAP_PLANS change from false to true and caused a number of issues with sub-optimal execution plans.

Another possible trap for the unwary ...

Cheers

Richard
----- Original Message -----
To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com> Sent: Thursday, October 02, 2003 2:54 AM

> One of the undocumented init.ora parameters that changed from 8 to 9 is
> "_UNNEST_SUBQUERY" (from false to true). You could try if that is the
> culprit. Of course, since it is an undocumented parameter, get the
blessing
> from Oracle support before using it in a production database.
>
> At 10:09 AM 10/1/2003, you wrote:
> >Joan, what is the difference in the plans? What specific feature
> >made the difference? Are the values of
> >optimizer_index_cost_adj and optimizer_index_caching same on both
> >versions? How about histograms? What is with
> >db_file_multiblock_read_count,sort_area_size and hash_area_size? Is
> >everything same as in 8i? May be setting of those parameters can be
> >tweaked to your benefit?
> >
> >On Wed, 2003-10-01 at 11:54, Joan Hsieh wrote:
> > > Kirti,
> > >
> > > I had upgraded a database from 8.1.7.4 to 9.2.0.4. Before the upgrade,
> > > performance is good. After upgrade, one query run time from 2 min to
12
> > > hours. Of course, I re-analyzed all tables and indexes. The explain
plan
> > > changed from hash join to nested-loop. All the parameters are same. So
I
> > > have to put optimized_feature_enable=8.1.7 to make run normal as
usual.
> > > I hate to disable the new feature, but no choose.
>
> 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
>
> Fat City Network Services -- 858-538-5051 http://www.fatcity.com
> San Diego, California -- Mailing list and web hosting services
> ---------------------------------------------------------------------
> To REMOVE yourself from this mailing list, send an E-Mail message
> to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in
> the message BODY, include a line containing: UNSUB ORACLE-L
> (or the name of mailing list you want to be removed from). You may
> also send the HELP command for other information (like subscribing).
>

-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.net
-- 
Author: Richard Foote
  INET: richard.foote_at_bigpond.com

Fat City Network Services    -- 858-538-5051 http://www.fatcity.com
San Diego, California        -- Mailing list and web hosting services
---------------------------------------------------------------------
To REMOVE yourself from this mailing list, send an E-Mail message
to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in
the message BODY, include a line containing: UNSUB ORACLE-L
(or the name of mailing list you want to be removed from).  You may
also send the HELP command for other information (like subscribing).