Re: Fwd: Re: Really deleting system statistics?
- From: Peter Alteheld <palteheld@xxxxxxxx>
- To: amit poddar <amit.poddar@xxxxxxxx>
- Date: Thu, 12 May 2005 08:47:07 +0200 (CEST)
Well, I see different costs in 10g, when I have no system statistics and switch
optimizer models.
For example: do a full table scan with select count(object_id) from big_table
(table from Tom Kyte's Effective Oracle by Design) - with IO model costs=5630,
with CPU model costs = 13065
Peter
amit poddar <amit.poddar@xxxxxxxx> wrote:
I thought Oracle would use the IO model in absence of system statistics
(default behaviour in 9i) ?
thanks
amit
Peter Alteheld wrote:
>Hi,
>
>I wanted to learn about the cpu model behaviour when no system statistics are
>available. That is different from the io model.
>
>Peter
>amit poddar wrote:
>How about settting
>
>_optimizer_cost_model to *io
>
>SQL> alter session set "_optimizer_cost_model"=abc;
>ERROR:
>ORA-00096: invalid value ABC for parameter _optimizer_cost_model, must
>be from
>among choose, io, cpu
>
>
>
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