Re: buffer advisor
- From: Jeremy Schneider <jeremy.schneider@xxxxxxxxxxxxxx>
- To: Ls Cheng <exriscer@xxxxxxxxx>
- Date: Fri, 5 Sep 2014 07:37:55 -0400
On Thu, Sep 4, 2014 at 4:37 PM, Ls Cheng <exriscer@xxxxxxxxx> wrote:
>
> Has anyone used buffer cache advisory in 10g or 11g to size a production
> buffer cache? If so how good is the advisor recommending the cache size?
> Did the recommended cache size meet the physical reads reduction goal?
>
I regularly reference the advisory, figuring that it will give some useful
information about the impact of changing the cache size. But I usually
compliment that with some knowledge of the app. (what's driving I/O now?
how large are the segments? what's the small table threshold going to
be?) Seems to me like it always lays out a fairly smooth curve, so it's
just one person's opinion about where that curve is. In my experience I
don't think it's been very accurate for any significant change (50% or more
either direction).
Lately I've gotten a lot of benefit by configuring a large keep cache for
the handful of I/O intensive segments bigger than the small table size but
small enough to fit in the buffer cache. ymmv.
-J
--
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