Re: optimizer_ ???

From: Niall Litchfield <niall.litchfield_at_gmail.com>
Date: Tue, 26 Apr 2005 16:13:26 +0100
Message-ID: <7765c8970504260813b47842b@mail.gmail.com>

On 4/26/05, Christian Antognini <Christian.Antognini_at_trivadis.com> wrote:
> Hi Niall

>=20


> >> How huge can the impact on the response time be by tweaking oic?

> >> Precisely: do you know of an example where you gain a response

> >> time reduction which is very impressive?

> >

> >I had cause to Google this just recently and I can't find any examples
> >of changes to response time.

>=20
> It's really easy to build such an example... here a very simple one...
<snip eg>

> As you can see by switching OIC from its default value to 90, which his o=
ne of my preferred silver bullets ;-), the query is much slower (factors, n= ot percents...).
>=20
> Of course with a higher number of joined tables and more data the differe=
nces could be much much higher!

Ah yes, indeed I have just such an example in my recent blog on oic and oica (it was oica that had a similar effect for us) :) The original question though was after an example of improved performance rather than changed plans, and it was that that I couldn't find anywhere (and found very difficult to create). I find it very easy to reduce the performance of Oracle queries - I do it frequently and one of the best ways is by messing with parameters and discovering by the phone ringing which users you've managed to hack off today.

--=20
Niall Litchfield
Oracle DBA
http://www.niall.litchfield.dial.pipex.com

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Received on Tue Apr 26 2005 - 11:23:29 CDT