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[Onkar Kamat]

Hi Experts,
I need some help in understanding little's Law in performance testing.

i have got the formula as
N= X * ( Z + R )
Where N=number of users
      X= Throughput
      Z Think time
      R=Responce time

My questions are

1) From the Loadrunner graph we get throughput in bytes/sec do we have to user this   value or we have to use "Transaction per sec" value as throughput?
2) Here "Z" is the Thinktime used in the whole script or the thinktime that is applicable only to the respective transaction?
3) if my scenario has a script in which there are more than one transactions. how to calculate the value of "N" using above formula?

As i am new to performance testing kindly help me understanding this law better........


 

[Shay Ginsbourg]

Little's law - From Wikipedia, the free encyclopedia -

In queueing theory, Little's result, theorem, lemma, or law says:
The long-term average number of customers in a stable system L is equal to the long-term average arrival rate, λ, multiplied by the long-term average time a customer spends in the system, W, or:

L = λW

Although it looks intuitively reasonable, it's a quite remarkable result, as it implies that this behavior is entirely independent of any of the detailed probability distributions involved, and hence requires no assumptions about the schedule according to which customers arrive or are serviced.

Little's law can be used in software performance testing to ensure that the observed performance results are not due to bottlenecks imposed by the testing apparatus.

So, the transactions are not relevant here and the value of "transaction per sec" is not the throughput.