Re: buffer advisor
Date: Fri, 5 Sep 2014 07:37:55 -0400
Message-ID: <CA+fnDAbWRb8d3C=4TLg5oeq-E+ePWS_VaRJyujUN4eNEhiUCpg_at_mail.gmail.com>
On Thu, Sep 4, 2014 at 4:37 PM, Ls Cheng <exriscer_at_gmail.com> 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
-- http://about.me/jeremy_schneider -- http://www.freelists.org/webpage/oracle-lReceived on Fri Sep 05 2014 - 13:37:55 CEST