RE: Statspack ratios help

  • From: "Allen, Brandon" <Brandon.Allen@xxxxxxxxxxx>
  • To: <bunjibry@xxxxxxxxx>, "Oracle-L" <oracle-l@xxxxxxxxxxxxx>
  • Date: Tue, 6 Jun 2006 12:54:55 -0700

Generally you want to read from memory rather than disk, but when your
BHR is 100%, that is sometimes an indicator that you have some
inefficient queries that are doing way too many logical reads, which is
usually caused by use of an index where a full scan would be more
efficient.  It would take more data to confirm this is the case though.
A good place to start would be with looking at your top sql by buffer
gets (further down in the statspack report) and seeing if they are
performing more gets than they should.  In this case, it looks like the
high BHR is more attributable to the fact that his physical reads are
very low (.39/sec), rather than his logical reads being too high, since
26K/sec and 510/transaction isn't really unusual, so he probably just
has a small data set that is fitting entirely in memory.  Hard to tell
anything with certainty from the limited info provided, just some
guesses.
 
Regards,
Brandon
 
 

________________________________

From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Bryan Wells
Sent: Tuesday, June 06, 2006 12:39 PM
To: Oracle-L
Subject: Re: Statspack ratios help


As a Jr. wanting to be Sr. (someday) I have to ask the stupid questions:
 
why is Buffer % bad?  Dont you want 100% buffer cache hit vs. 100% disk
i/o?

 

Privileged/Confidential Information may be contained in this message or 
attachments hereto. Please advise immediately if you or your employer do not 
consent to Internet email for messages of this kind. Opinions, conclusions and 
other information in this message that do not relate to the official business 
of this company shall be understood as neither given nor endorsed by it.

Other related posts: