Re: Parameter to influence Oracle's Idea of IO Cost?

Robert Klemme wrote:
>
> Hi,
>
> this is on 10.2.0.1.0. I think I remember that there is a parameter
> that will affect how Oracle costs IO but can't seem to find it (searched
> DB Reference, Performance Tuning Guide, PL/SQL Package Reference, Web).
> Does my memory fail me?
>
> Do you know other ways to influence how Oracle costs single block reads
> vs. multi block reads (apart from DB_FILE_MULTIBLOCK_READ_COUNT and
> hinting that is)? Thank you!
>
> Kind regards
>
> robert

short answer

• optimizer_*** parameters as suggested before - tend to scale costs down and result in more ties.
• system statistics as also suggested before - tend to scale costs up and reflect your real hardware, both of which are good, but take much more effort to collect in a way that is reasonable.

My guess is you might well get better immediate success with the optimizer_... parameters, but better longer term success with system stats.

-- 
Niall Litchfield
Oracle DBA
http://www.orawin.info/services