Re: Correct way to accuse BCHR tuning method (Was: Hit ratio)

I think Dave Ensor, at the recent UKOUG conference, called it his "portable tuning kit":

select elapsed_time, cpu_time
  from v$sql
order by elapsed_time;

Mogens

Connor McDonald wrote:

>Yep.
>
>Simple example: Even though it seems to be sometimes a
>little on the 'random' side, the ELAPSED_TIME column
>on V$SQL in v9 is an absolute god send...
>
>Cheers
>Connor
>
> --- Mogens_Nørgaard <mln_at_miracleas.dk> wrote: > And I
>think it's important to realise that ratios
>
>
>>are useless as a
>>starting point in the tuning process on any system,
>>not only Oracle.
>>Most OS'es and databases use not instrumented
>>correctly to deal with
>>response time measurements (makes you wonder: If
>>response TIME is what
>>matters, how can you then not measure exactly that -
>>time?) - so in the
>>other worlds (Unix, VMS, Windows, SQL Server, MySQL,
>>DB2....) people
>>still beleive in the ratios because they have
>>nothing better.
>>
>>Mogens
>>
>>Anjo Kolk wrote:
>>
>>
>>
>>>BCHR tuning is useless as a starting point in the
>>>
>>>
>>tuning process.
>>
>>
>>>Anjo.
>>>
>>>-----Original Message-----
>>>Yong Huang
>>>Sent: Wednesday, December 24, 2003 6:09 PM
>>>To: Multiple recipients of list ORACLE-L
>>>
>>>
>>>[This message is not technical, but educational.
>>>
>>>
>>Readers interested in
>>
>>
>>>technical info only may want to skip]
>>>
>>>Hi, Cary and Gopal,
>>>
>>>My last message is misunderstood. Nowadays most
>>>
>>>
>>DBAs that still use
>>
>>
>>>buffer cache hit ratio as a primary performance
>>>
>>>
>>tuning method are those
>>
>>
>>>that rarely browse public forums. When we convince
>>>
>>>
>>them that's a wrong
>>
>>
>>>method, we should not say "Look. I can bump up BCHR
>>>
>>>
>>to an arbitrary
>>
>>
>>>value". If he doesn't think, he'll say "Indeed. If
>>>
>>>
>>I can get any value,
>>
>>
>>>it must be rubbish". But if he's a logical person
>>>
>>>
>>and thinks for a few
>>
>>
>>>minutes, he'll say "It's unfair to run that
>>>
>>>
>>choose_a_hit_ratio program
>>
>>
>>>to get an arbitrary hit ratio and say the method is
>>>
>>>
>>wrong, because you
>>
>>
>>>can use the same logic to write a program to get an
>>>
>>>
>>arbitrary library
>>
>>
>>>cache hit ratio, OS in-core inode cache hit ratio
>>>
>>>
>>or directory name
>>
>>
>>>cache hit..."
>>>
>>>My last message is not meant to revive the outdated
>>>
>>>
>>and probably never
>>
>>
>>>correct tuning method. Instead it's meant to let
>>>
>>>
>>oracle-l members know
>>
>>
>>>that when you need to convince those DBAs that
>>>
>>>
>>still use that method,
>>
>>
>>>you need to accuse the BCHR method for correct
>>>
>>>
>>reason, namely, BCHR does
>>
>>
>>>not contain sufficient information for tuning, not
>>>
>>>
>>because you can raise
>>
>>
>>>its value by constantly scanning a table in Oracle;
>>>
>>>
>>you won't be able to
>>
>>
>>>convince some stubbon DBAs who enjoy thinking in a
>>>
>>>
>>quiet place.
>>
>>
>>>I agree that "It's not the ratio that needs
>>>
>>>
>>condemning, it's the advice
>>
>>
>>>about..." What I disagree is the wrong educational
>>>
>>>
>>tool people on public
>>
>>
>>>forums have recently used again and again to show
>>>
>>>
>>the inadequacy of the
>>
>>
>>>BCHR tuning method.
>>>
>>>Yong Huang
>>>
>>>__________________________________
>>>Do you Yahoo!?
>>>New Yahoo! Photos - easier uploading and sharing.
>>>http://photos.yahoo.com/
>>>
>>>
>>>
>>>
>>--
>>Please see the official ORACLE-L FAQ:
>>http://www.orafaq.net
>>--
>>Author: =?ISO-8859-1?Q?Mogens_N=F8rgaard?=
>> INET: mln_at_miracleas.dk
>>
>>Fat City Network Services -- 858-538-5051
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>
>=====
>Connor McDonald
>web: http://www.oracledba.co.uk
>web: http://www.oaktable.net
>email: connor_mcdonald_at_yahoo.com
>
>"GIVE a man a fish and he will eat for a day. But TEACH him how to fish, and...he will sit in a boat and drink beer all day"
>
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-- 
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  INET: mln_at_miracleas.dk

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