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"Geomancer" <pharfromhome_at_hotmail.com> wrote in message
news:cf90fb89.0311210459.57364286_at_posting.google.com...
> Again, my problem was with this statement:
>
> "A hit ratio in excess of 99% often indicates the existence of
> extremely inefficient SQL"
>
> I was simply hoping that someone could explain why a stallar BHR often
> indicates poorly optimized SQL. Can someone explain the "OFTEN" part
> here?
Ways to get a high hit ratio.
I think the comment (and bear in mind that Cary works almost exclusively with systems with performance problems) is really saying that when you have spectacularly high hit ratios it is most likely that point 2 is happening rather than point 1. You will *usually* get this where
you are doing nested loops joins rather than a merge or hash join. you are repeatedly issuing the same sql with different literals, or in a loop rather than using array fetches.
-- Niall Litchfield Oracle DBA Audit Commission UKReceived on Fri Nov 21 2003 - 07:14:30 CST