Re: JDBC connection pool and logon triggers
- From: Mladen Gogala <mladen@xxxxxxxxxxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Fri, 28 May 2004 11:05:21 -0400
On 05/28/2004 10:45:39 AM, Reginald.W.Bailey@xxxxxxxxxxxx wrote:
>
> Mladen:
>
> What is BCHR?
>
Reginald, I apologize for making a jovial reference without explaining it. BCHR
stands for
"Buffer Cache Hit Ratio" and is sometimes used as an ultimate measure of system
performance,
much in the same fashion as when witch doctors predict weather. This measure
was originally
introduced by Oracle, who even devoted a chapter the tuning book devoted to
tuning the
BCHR. There were 2 tables (one of them was X$KCBCBH and I forgot the name of
the other one)
which DBA was supposed to use to get the BCHR sufficiently high. The whole
alchemy went on
until another esteemed member of this list, Mr. Anjo Kolk, asked a completely
illogical and
outrageous question: how do you tune an application, if you don't know what the
application
is waiting for and how the time is spent? He also developed so called "wait
interface" and
there was a very thick document, available on Metalink, describing oracle wait
events for
Oracle7. The whole philosophy was taken to the new heights by Cary Millsap in
his book
"Optimizing Oracle Performance".
--
Mladen Gogala
Oracle DBA
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