Re: Cache Hit Ratio from system views

On Wed, 08 Aug 2007 12:02:46 -0700, Teresa Masino <teresa.masino_at_peninsula.org> wrote:

>
>Alone, yea, but they can sometimes be an indicator that an instance
>needs attention.

Do you really think so? Yesterday I had a customer spouting flames because of a RAC database coming down to a crawl due to buffer busy waits in conjunction with both instances updating the same table over and over again.
Nothing to be seen from the BCHR.

But then of course BCHR is a MIPS (Meaningless Indicator of the Performance of the System).
Only good old Don Burleson makes people erroneously believe they can tune their database by throwing memory at the problem to crank up the BCHR.
Savy professionals (a favorite phrase of Don) know better.

-- 
Sybrand Bakker
Senior Oracle DBA