Oracle FAQ Your Portal to the Oracle Knowledge Grid
HOME | ASK QUESTION | ADD INFO | SEARCH | E-MAIL US
 

Home -> Community -> Usenet -> c.d.o.misc -> Re: Using a CBO Schema on an RBO Database

Re: Using a CBO Schema on an RBO Database

From: Peter van Rijn <p.vanrijnREMOVE_at_THISzhew.nl>
Date: Wed, 11 Dec 2002 10:43:15 +0100
Message-ID: <uve25u7srn8h6c@corp.supernews.com>


Hello Neil,

Yes, you are right. A few thoughts though. You say your 8i server is configured to use RBO. How? By setting optimzier_mode=rule in the init.ora? Or by setting it to choose and not having statistics?

If it is set to rule, and you DO have statistics still the RBO will be used (in 8.1.7 that is). This can be userruled by hints or by altering the session to opimtizer_goal=<anything but rule>. If it is set to choose, not having statistics will invoke RBO, else if you have statistics on ANY of the tables in a query CBO will be used.

Your DBA can play safe by setting optimizer_mode to rule, so that it's your responsibilty to alter the session or use hints.

hth,
Peter

"Neil Phillips" <nap23_at_talk21.com> schreef in bericht news:478af260.0212110109.619bb8e1_at_posting.google.com...
> Hi
>
> I am installing some software onto an 8i server which is configured to
> use the RBO. (This is becuase the only piece of software currently
> using this server has been optimised over the years to use RBO)
> I want to install some new objects onto this server to be used by my
> software.
> I want to create a new schema that will 'hold' all of my tables,
> procedures etc on this server. Idealy, I would like to use the CBO
> (mainly for function-based indexes) but the dba doesn't want me to
> anlayse any of my objects in my schema for fear it may upset the other
> schema the originl software belongs to and force that to use the CBO
> as well.
> Am I right in thinking that even if the schema the original software
> belongs to uses RBO, if I execute an Analyze Schema statement within
> my schema, only objects within my schema will be analysed and so only
> my schema will use the CBO. Everything else within the instance will
> remain unaffected by this and so will continue to use the RBO? Is this
> true? Has anyone else come across this problem?(The reason I say that
> is SYS uses RBO but all of the schemas I use on mu dev server are
> analaysed and so use CBO and I have never run into any problmes doing
> this.)
>
> Any thoughts would be greatly appreciated.
>
> Many Thanks
>
> Neil
Received on Wed Dec 11 2002 - 03:43:15 CST

Original text of this message

HOME | ASK QUESTION | ADD INFO | SEARCH | E-MAIL US