Re: Cache Hit Ratio from system views

"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.

Cheers

Richard Received on Thu Aug 30 2007 - 03:41:32 CDT