Re: very low hit ratio

From: Howard J. Rogers <hjr_at_dizwell.com>
Date: Thu, 25 Mar 2004 11:58:37 +1100
Message-ID: <40622ec2$0$8357$afc38c87@news.optusnet.com.au>

"JW" <jwu_at_nctr.fda.gov> wrote in message news:f4d9400.0403241310.150b1fb4_at_posting.google.com...
> we have a data warehouse type of database and I noticed that buffer
> cache hit ratio is very low: db block gets 37,173,962; consistent gets
> 349,994,093; physical reads 888,341,652. Is this normal in a
> datawarehouse environment? Thanks.

Who cares?

Are your users complaining about performance?

If not, then your hit ratio is just fine and dandy, whatever it happens to be.

The more general point here is that, Don Burleson and TUSC notwithstanding, the buffer cache hit ratio is an absolutely abysmal way of tuning anything. It can sometimes offer a useful corollary to other statistics; to allow you to distinguish between two otherwise equally plausible causes for, for example, free buffer waits. But as a performance tuning goal in its own right? Furgedaboudit.

Regards
HJR Received on Wed Mar 24 2004 - 18:58:37 CST