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

On May 9, 6:48 am, Robert Klemme <shortcut..._at_googlemail.com> 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

See Tom Kyte's Effective Oracle by Design chapter 6 ... OPTIMIZER_INDEX_CACHING and OPTIMIZER_INDEX_COST_ADJ I think are what you are referring to.

Tom's not a big believer in silver bullets or giving blind recommendations but notes the default settings may not be good for many systems and also notes that perhaps data warehouses might benefit from values of 0 and 100 for those but oltp workloads might find 90 and 25 more appropriate ( perhaps ). Received on Wed May 09 2007 - 06:12:03 CDT