Hello All, I did some work using QT and Oracle in 2002 or 2003 (just 2 - 3 years after I finished college). At that time I was brave enough to starting building a queuing model of major Oracle components - of course if was very complex and even simulation tools I used for it was unable to give me results close to my expectation. Thankfully I read Cary's book and early Craig papers about it and decide that simple M/M/n should work for 90 % of capacity planing exercises. As Andrey mentioned above we can use G/G/n instead of M/M/n but it will be more complex. In terms of exponentiation arrival rate I think is more important to be use that metric that we will use will be independent and identically distributed. Probably title of the book is not a best one for science brains but I would recommend to read this book if you are interested in modeling system - "The art of computer system performance analysis" by Raj Jain - http://www.amazon.com/The-Computer-Systems-Performance-Analysis/dp/0471503363 - not a newest one but math is math. regards, -- Marcin Przepiorowski http://oracleprof.blogspot.com On Sun, Mar 16, 2014 at 3:51 PM, Николаев Андрей Серапионович < Andrey.Nikolaev@xxxxxxxx> wrote: > Hello! > >I am asking if anyone has successfully used queuing theory in Oracle ... > > This is very interesting and still developing research area. Typically, > the Oracle database internal algorithms are much more complex then the > standard QT models. > > In my opinion, the QT provides us with phenomenological background about > the observables (utilization, arrival rate, queue length, wait time, > service demand ...) and their interdependences (Little's Law, (1-u)^-1 > behavior, ...) > > This result in the phenomenological rules such as: Amdahl's law, Universal > Scaling law by Neil Gunther, "Magic of 2" by Cary Millsap, ... > All the above allows the performance capacity planning and predicting. > > In addition to previously discussed in this thread the classical books by > Cary Millsap, Craig Shallahammer, and the Hotsos presentations by Henry > Poras, I would like to recommend the inspiring books by Dr. Neil Gunther. > > > >I guess to use M/M/n we just have to assume certain database metrics are > >exponentially distributed such as ... > >If not we arent suppose to use queueing theory because it is based on > >exponentially distributed data. > > Unless you encounter a heavy tailed distribution, the Law of large numbers > is on your side. > Approximate G/G/n formulas show behaviors close to the corresponding M/M/n > formulas and generally differ only by multipliers. > Therefore, you can use M/M/n expressions for estimations. > > However, Dr. Neil Gunther at Hotsos 2012 demonstrated that the heavy > tailed distributions and the "fractal behavior" do exist in Oracle world. > Such cases require more complicated treatment. > > >Maybe some wait events about latches/mutex/... can be seen as pure > QueueTime... > > Despite the classical QT works well for estimations, the detailed > investigation of the queuing properties for even the simplest Oracle > objects, such as mutexes is more complicated. > > For example, the "wait" in Oracle has the different meaning then wait in > Queuing Theory. Even the "average wait time" has another definition. > > Some time ago, I presented about Oracle mutexes and the corresponding > queuing models. > If you are interesting, you can find the article at > http://arxiv.org/abs/1212.6640 > (Warning: Math ahead) > > With Best Regards > Andrey Nikolaev > http://andreynikolaev.wordpress.com > > > -- > //www.freelists.org/webpage/oracle-l > > >