Re: Queueing Theory in Oracle

From: Karl Arao <karlarao_at_gmail.com>
Date: Tue, 11 Mar 2014 10:51:23 -0500
Message-ID: <CACNsJnfZ7m630XfcSmoXa7h6zeU3rAADJ2b9m9Me47bc-qNjKA_at_mail.gmail.com>

I've read both of the books, and I love them. On this link are my notes - http://goo.gl/b8aNOj
Although queueing theory is pretty cool, I find the chapter on regression analysis more suited for real world but the queueing theory chapter builds a nice foundation of ResponseTime=ServiceTime+QueueTime which is from a practical use case point of view the Performance Page you've got all of that components in a nice pretty dashboard broken down into wait class with CPU as your service time and everything else is QueueTime.

For the regression analysis on the link (r2project), what I did is rank the independent values (x) that has the high correlation coefficient and make use of that to forecast the dependent value (y). Also the page 8 of this paper http://www.slideshare.net/karlarao/where-didmycpugo also gives you more insights about the "more CPUs, faster CPUs, more and faster CPUs" section of the book, I think it's page 32.

-Karl

On Tue, Mar 11, 2014 at 9:46 AM, Ls Cheng <exriscer_at_gmail.com> wrote:

> Hi
>
> I have been reading Craig's book and Cary's book (chapter 9) for the last
> 2 weeks, the theory in the books look great but when I tried to start using
> in the real world it the questions started to appear.
>
> For example, arrival rate, what arrival rate in Oracle is exponentially
> distributed......? Cary says logical reads in his book but I just dont see
> how can that be possible by using the database metric (for example system
> metric such as Logical Reads Per Sec or Logical Reads Per User Call).
> Craig's book I dont even mention a useful database metric (I havent
> finished the book yet so I might have missed if he has said so), the book
> just uses all the time the work unit transaction per second.
>
> Both book provide a queueing theory workbook but they are useless from
> database metric point of view since no metric is poisson or exponential
> distributed (again I am not able to see it, if someone can please advice).
>
> But Jonathan you just mention "buffer gets per user call" which is similar
> to Logical Reads Per User Call from v$sysmetric, why do you think that is
> exponentially distributed :-?
>
>
> Thanks
>
>
>
>
> On Tue, Mar 11, 2014 at 3:30 PM, Jonathan Lewis <
> jonathan_at_jlcomp.demon.co.uk> wrote:
>
>>
>> It's an interesting question - and I don't think you can find a current
>> metric that would help unless you started doing something a little clever
>> with ASH.
>>
>> In an OLTP system something like 'buffer gets per user call" would
>> probably be a reasonable fit - but there's no capture at that granularity.
>> Similarly disc I/O requests per call might be appropriate. Then there are
>> things like disk I/O requests per disc per second. But every possibility I
>> think of requires too fine a level of granularity unless you can find a way
>> to construct a valid model from the samples in v$active_session_history.
>>
>>
>>
>> Regards
>> Jonathan Lewis
>> http://jonathanlewis.wordpress.com
>> _at_jloracle
>> ------------------------------
>> *From:* oracle-l-bounce_at_freelists.org [oracle-l-bounce_at_freelists.org] on
>> behalf of Ls Cheng [exriscer_at_gmail.com]
>> *Sent:* 11 March 2014 14:20
>> *To:* Paul Houghton
>> *Cc:* Oracle Mailinglist
>> *Subject:* Re: Queueing Theory in Oracle
>>
>> Hi
>>
>> I have had a quick read, I think the link you posted talks about queue
>> time but not about queueing theory such as a M/M/n model. The problem is I
>> am not able to find a database metric that is exponential distributed which
>> allows us to use the M/M/n queueing theory.
>>
>> Thanks
>>
>>
>>
>> On Tue, Mar 11, 2014 at 3:16 PM, Paul Houghton <
>> Paul.Houghton_at_admin.cam.ac.uk> wrote:
>>
>>> Craig Shallahamer talks about queuing theory in the following blog post.
>>>
>>>
>>> http://shallahamer-orapub.blogspot.co.uk/2011/08/why-tuning-oracle-works-and-modeling-it.html
>>>
>>> I hope this is helpful
>>>
>>> PaulH
>>>
>>>
>>
>

-- 
Karl Arao
Blog: karlarao.wordpress.com
Wiki: karlarao.tiddlyspot.com
Twitter: _at_karlarao <http://twitter.com/karlarao>

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Received on Tue Mar 11 2014 - 16:51:23 CET