Re: Cache Hit Ratio from system views

On Sep 3, 7:19 pm, Niall Litchfield <niall.litchfi..._at_gmail.com> wrote:

>
> > BHCR shows disk i/o percentage. An important indicator for buffer cache
> > tuning.
>
> So how exactly would you use it? If BCHR falls below a certain value
> increase one or more of the pool sizes? If it rises above a certain
> value reduce them?

I think everyone knows where I stand on this subject. However, I'd just like to point out that these words: "The buffer cache hit ratio can be used to verify the physical I/O as predicted by V$DB_CACHE_ADVICE."
are even as we write in the relevant section of the performance tuning guide of oracle 10g, specifically in here: http://download.oracle.com/docs/cd/B19306_01/server.102/b14211/memory.htm#sthref504

Pity this thing is to this day still promoted as a relevant performance
measurement tool. Now: if this was v6 and there was nothing else available, I can understand why we'd still talk about it. Nowadays? Let's move on, much better stuff to look at.

> shouldn't be news given that it was first described and demonstrated
> by Knuth when I was 4 (and I'm ten times that age this year). The more

hippo birdie in advance! or late? Anyways: big 4-0, eh? Congrats! Received on Wed Sep 05 2007 - 23:33:54 CDT