Re: Queueing Theory in Oracle

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
>>
>>
>

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