Re: CBO doesn't work!

I appreciate your help in giving me a starting point. I did look at the parameters you suggested, but they are actually set quite low.

 db_file_multiblock_read_count	=8
    sort_area_size	= 65536
    hash_area_size	= 131072

We have generated histograms, and the values that are passed in for am_vend_id (304,2876) are parameters passed in by the application, and the RBO seems to outperform the CBO for any values passed in. So it seems that I am still stumped.
Thanks for the help.

zp

In article <979085948.15666.1.nnrp-12.9e984b29_at_news.demon.co.uk>,   "Jonathan Lewis" <jonathan_at_jlcomp.demon.co.uk> wrote:
>
> Look in particular at your values in
> the init.ora file for:
>
> db_file_multiblock_read_count
> sort_area_size
> hash_area_size
>
> You may have persuaded the CBO that it
> is very cheap to scan and sort large tables
> then hash the results.
>
> Also (for this case) are 304,2876 values for
> AM_VEND_ID which have a particularly small
> set of results compared to other values for
> AM_VEND_ID. If so are you generating column
> histograms to let Oracle know about special
> cases ?
>

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http://www.deja.com/ Received on Wed Jan 10 2001 - 10:09:30 CST