Re: Cache Hit Ratio from system views

"Richard Foote" <richard.foote_at_nospam.bigpond.com> wrote in message news:0pvBi.28320$4A1.3414_at_news-server.bigpond.net.au...
>
> "Bob Jones" <email_at_me.not> wrote in message
> news:2WpBi.51277$YL5.24111_at_newssvr29.news.prodigy.net...
>>
>> "Richard Foote" <richard.foote_at_nospam.bigpond.com> wrote in message
>> news:cXdBi.27614$4A1.19426_at_news-server.bigpond.net.au...
>>> "Bob Jones" <email_at_me.not> wrote in message
>>> news:7d_Ai.4071$JD.3351_at_newssvr21.news.prodigy.net...
>>>>
>>>> "Richard Foote" <richard.foote_at_nospam.bigpond.com> wrote in message
>>>> news:seAAi.26732$4A1.22707_at_news-server.bigpond.net.au...
>>>>> "Bob Jones" <email_at_me.not> wrote in message
>>>>> news:mOnAi.236$ZA5.16_at_nlpi068.nbdc.sbc.com...
>>>>>>
>>>>>> "Richard Foote" <richard.foote_at_nospam.bigpond.com> wrote in message
>>>>>> news:2_Wyi.24466$4A1.1328_at_news-server.bigpond.net.au...
>>>>>>>
>>>>>>> "Bob Jones" <email_at_me.not> wrote in message
>>>>>>> news:kOtyi.50198$YL5.8637_at_newssvr29.news.prodigy.net...
>>>>>>>>
>>>>>>>> High BCHR is always better than low - provided everything else
>>>>>>>> being equal. If BCHR is useless for the stated reasons, no other
>>>>>>>> indicator would be useful.
>>>>>>>
>>>>>>> This I'm afraid is where you're fundamentally incorrect.
>>>>>>>
>>>>>>> A high BCHR can mean your database is on life support, struggling to
>>>>>>> cope with exessive LIOs due to inefficient SQL with users staring at
>>>>>>> an hourglass rather than returned data.
>>>>>>>
>>>>>>> A BCHR that has increased can mean your database has suddenly hit
>>>>>>> significant performance issues. Or it can mean things have improved.
>>>>>>> Or it can mean response times remain unaffected.
>>>>>>>
>>>>>>> A BCHR that has reduced can mean your database has suddenly hit
>>>>>>> significant performance issues. Or it can mean things have improved
>>>>>>> (yes, improved because that crippling transaction that was
>>>>>>> previously performing poorly due to massively exessive LIOs has been
>>>>>>> fixed, reducing the overall BCHR) . Or it can mean response times
>>>>>>> remain unaffected.
>>>>>>>
>>>>>>> Not much of an indicator is it ?
>>>>>>>
>>>>>>> But saying that a BCHR is *always* better than a low is just plain
>>>>>>> wrong wrong wrong ...
>>>>>>>
>>>>>>
>>>>>> Didn't I repeatedly say "provided everything else being equal"?
>>>>>>
>>>>>
>>>>> And how precisely do you determine that everything else indeed is
>>>>> equal ? Most databases don't exactly remain equal ...
>>>>>
>>>>
>>>> No, they do not. That's why you do not look at BCHR alone, as I have
>>>> said before.
>>>
>>> So what else do you look at in conjunction with the BCHR ?
>>>
>>> Interestingly, you never answer any of the questions and you never give
>>> any examples of why you consider the BCHR to be such a fantastic
>>> indicator. And yes, I have read *all* your contributions to this
>>> discussion ...
>>>
>>> So how about you at least attempt to justify your claim that the BCHR is
>>> "a very meaningful indicator". How do you actually use the BCHR in a
>>> meaningful manner ? So you look at the BCHR and ..., and what ?
>>>
>>> And when do you look at these other "whatevers" in conjunction with the
>>> BCHR ? When the BCHR increases, what else do you check ? And when the
>>> BCHR decreases, what else do you check and how do these checks differ
>>> from when the BCHR increases ? And when the BCHR remains the same, what
>>> else do you check and how do these checks differ from when the BCHR
>>> increases or decreases ?
>>>
>>> Remember, it's your claim that the BCHR is "a very meaningful
>>> indicator", well show us ?
>>>
>>> If you can ....
>>>
>>>>
>>>>> And when precisely do you check if everything else is equal with this
>>>>> "very meaningful indicator" of yours ? When the BCHR increases ? When
>>>>> the BCHR decreases ? When the BCHR remains the same ?
>>>>>
>>>>
>>>> Try asking yourself the same questions about any other indicators you
>>>> consider meaningful. The question here is not how to determine if
>>>> everything else is equal. It is about whether BCHR means anything if
>>>> everything else is equal.
>>>
>>> Please, if everything else is equal, how can the BCHR change ? How can a
>>> high BCHR always be better than a low BCHR, everything being equal when
>>> having a higher BCHR can only mean things are not equal by definition,
>>> else the BCHR would be the same ? Right ?
>>>
>>> Can you please explain how this is possible, having a higher BCHR with
>>> everything being equal, at least attempt some kinda description of what
>>> "everything else" means, at least attempt to justify this somewhat
>>> bizarre claim ...
>>>
>>> If you can ...
>>>
>>> Again I go back to my initial set of questions. If your BCHR were to
>>> increase from (say) 95% to (say) 99.9%, if this very meaningful
>>> indicator were to change in this manner, what else do you check to
>>> ensure that things are really better, that the higher BCHR is actually a
>>> good thing, that all these mysterious "things" are indeed equal ?
>>>
>>> And why wouldn't you need to check these other indicators when the BCHR
>>> decreases ?
>>>
>>> And why wouldn't you need to check these things if the BCHR remains the
>>> same ?
>>>
>>> If you can't answer these rather basic questions is a vaguely meaningful
>>> manner, then ummmm, game over I think.
>>>
>>> Go on, answer these questions, dare ya !!
>>>
>>> If you can ...
>>>
>>
>> Wow, that is a lot of questions for a simple concept. Apparently someone
>> has not been paying attention. I am not sure why different people keep
>> asking questions that are either irrelevant or have been answered.
>
> Oh dear, the fact you think these questions irrelevant and you're not able
> to answer any of them, not a one, not even make a teeny weeny attempt, is
> "a very meaningful indicator" that you have absolutely no idea.
>
> Everything else being equal of course.
>
> Oh I forget, you've already answered them in some other universe, blah
> blah blah blah ...
>
> Like I predicted, game over.
>
> You lose.
>

Yes, I have lost in educating the logically challenged. Received on Thu Aug 30 2007 - 23:05:59 CDT