Re: Buffer cache Hit - Perf overview

Hi Sundar,

> I was used to near 99% Hit on 7.3, managed 98% 0n 8.1.5
> But can't seem to get above 90% Buffer cache hit on 8.1.6. 8i.
> Has anyone managed to get near or above 95%.
> Response from my website I have configured (creativebase.com) is good from the outside world but as a DBA I am not happy for the DB. Anybody using the similar config ? Results ? Comments appreciated.

/SOAPBOX ON, FLAMEPROOF SUIT ON This is one myth that is being broken (and not too soon!). You (and many of us) need to unlearn the notion that a 99% hit ratio is not necessarily GOOD. As you yourself stated, the response is good, so what's the problem??

/SOAPBOX OFF, FLAMEPROOF SUIT OFF Have a look at V$SYSTEM_EVENT and look at what the Database has been waiting for the most (set TIMED_STATISTICS=TRUE if not yet). From there, drill down to V$SESSION_EVENT and V$SESSION_WAIT to see what if any sessions are waiting on, and take it from there. There is no point in achieving 99% buffer hits if a session is waiting on a particular hot-spot object.

A good description of what this 'Wait Interface' (by Mogens Norgaard) is all about is described in a paper in Cary Millsap's Hotsos website (http://www.hotsos.com). It used to be free, but is now restricted. Worth subscribing to/reading.

(Sorry Gaja - stole your thunder!) Received on Thu Oct 26 2000 - 12:19:17 CDT