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Re: Cache Hit Ratio from system views

From: Bob Jones <email_at_me.not>
Date: Fri, 07 Sep 2007 00:54:00 GMT
Message-ID: <Ii1Ei.1929$>

<> wrote in message
> On Wed, 5 Sep 2007 21:12:05 -0500, "Bob Jones" <email_at_me.not> wrote:
>>"Niall Litchfield" <> wrote in message
>>> On 1 Sep, 01:29, "Bob Jones" <em..._at_me.not> wrote:
>>>> > If the BCHR is an objective indicator, please tell us of what you
>>>> > think
>>>> > it is an indicator, and how - specifically you would use it.
>>>> > Richard's
>>>> > indicator (as mine) is how long business transaction take. Definitely
>>>> > objective and relatively straightforward to use and understand.
>>>> 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?
>>>> As I said before, response time is not even a database metric.
>>> well no it isn't, it's a metric for the measurement of the performance
>>> of the application as experienced by the end-user. Round in my part of
>>> the world we install and use applications to support line of business
>>> transactions and it is those installations that we care about rather
>>> than the individual component. That's the primary reason that a metric
>>> derived from business usage makes most sense to me.
>>>>It is an effect not a cause.
>>> That's true enough, but breaking down the response time into it's
>>> component parts, say
>>> Time spent at web server
>>> Time spent in application server
>>> Time spent on network
>>> Time spent in DB.
>>> At a gross level gives you a much better tuning methodology than
>>> requests satisifed from cache for any given component of the stack.
>>> Producing an execution profile for the objects of interest really
>>> 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
>>> each of those tiers allow you to break down the response time
>>> components the better you chance of finding the problems.
>>>> With some people's logic here, even response time is
>>>> meaningless. 5 minutes response time can be better than 5 seconds
>>>> response
>>>> time, if it is doing 5000 times more work.
>>> That would likely depend on your requirements, in Richard's ATM
>>> analogy it would seem unlikely that many banks would prioritise
>>> keeping all their customers waiting 5 minutes to withdraw cash over
>>> allowing a smaller subset to be happy with their 5 second response. On
>>> the other hand if the per customer end of month statement takes 5
>>> seconds, but the batch process for 5000 takes 5 minutes then I know
>>> which I'd be scheduling in my month end process.
>>You are missing the point of this long thread. To avoid further branching
>>out to different topics, I would recommend reading it.
>>You are missing the point of this long thread. To avoid further branching
>>out to different topics, I would recommend reading it.
> This is probably a too difficult task for you, given your closed mind,
> and your earlier more unprofessional advices, as well as your
> unprofessional attitude.

Yes, it is way too difficult for a simple concept.

You talking to me about professionalism? This should be so hilarious. Received on Thu Sep 06 2007 - 19:54:00 CDT

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