Re: optimizer_ ???

  • From: Niall Litchfield <niall.litchfield@xxxxxxxxx>
  • To: Christian Antognini <Christian.Antognini@xxxxxxxxxxxx>
  • Date: Tue, 26 Apr 2005 16:13:26 +0100

On 4/26/05, Christian Antognini <Christian.Antognini@xxxxxxxxxxxx> wrote:
> Hi Niall
> >> 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.
> 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...).
> 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.

Niall Litchfield
Oracle DBA

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