Re: cost based optimization-Reposted

From: Connor McDonald <connor_mcdonald_at_yahoo.com>
Date: Tue, 07 Sep 1999 18:55:22 +0800
Message-ID: <37D4EF1A.6F1F@yahoo.com>

Anurag Minocha wrote:
>
> Hi,
> Nobody replied to my query , so again i am posting it. Matbe this time
> somebody will help me out.
>
> Thanks
> Anurag
>
> Anurag Minocha wrote:
>
> > Hi,
> > I am a little confused about Cost Based Optimization.Please help me out.
> >
> > 1.Does the cost based optimization work on those sql queries which dont
> > have hints specified in them.?
> >
> > 2. How frequently should the tables be analysed.
> >
> > Any help will be greatly appreciated.
> >
> > Thanks
> > anurag
> >
> > also reply to
> > anurag_at_synergy-infotech.com

CBO will be used if
a. there are statistics on the tables
b. if the optimizer_mode is set appropriately

In terms of when to analyze, remember what analyze is trying to do - namely attempting to provide a "measurement" of the way the data is distributed in your database. SO when the data distribution changes significantly you should re-analyze...

You may end with something like:

reference tables	- every month
transaction tables	- every week, plus after archiving

tables in read-only tablespace - once only

etc etc
--

---

Connor McDonald
"These views mine, no-one elses etc etc" connor_mcdonald_at_yahoo.com

"Some days you're the pigeon, and some days you're the statue." Received on Tue Sep 07 1999 - 05:55:22 CDT