Fred wrote:
> In article <4135cda9$0$5288$afc38c87_at_news.optusnet.com.au>,
> "Howard J. Rogers" <hjr_at_dizwell.com> wrote:
>
>
>>Fred wrote:
>>
>>
>>>It's early morning and I haven't had my usual dose of caffeine.
>>>
>>>A client is reporting their DB buffer cache is experiencing a hit rate
>>>of 156%. Normally, I wouldn't be alarmed by this bit of spurious data,
>>>but I would like to be able to explain to the customer how this might
>>>occur. Anyone?
>>>
>>>Fred
>>
>>What formula are they using to calculate that?
>>
>>It's a bit meaningless otherwise.
>>
>>I've never seen a hit ratio greater than 100% except when I attempt to
>>calculate it using mental arithmetic alone.
>>
>>Regards
>>HJR
>
>
> As best I can tell, the formula is simply:
>
> 1 - physical_reads / (consistent_gets + db_block_gets)
>
> The user is using a monitoring tool: VERITAS Savant, and the 156% hit
> rate is showing on the screen.
>
> Like you, I have never seen a hit ratio > 100%, but I have seen cases
> where there is data corruption in the V$ views in long-running instances
> (this was noted in MetaLink a while back). I wonder if this might be the
> case?
>
> Fred
From my experience ... another reason not to use Veritas but I'm
certainly open to any sage advice from any sage out there.
--
Daniel A. Morgan
University of Washington
damorgan_at_x.washington.edu
(replace 'x' with 'u' to respond)
Received on Wed Sep 01 2004 - 23:24:05 CDT
