What is Little's law?

 Little's Law:

Little's law is quite simple and intuitively appealing.

The law states that the average number of customers in a system (over some time interval), N, is equal to their average arrival rate, X, multiplied by their average time in the system, R.

N = X . R (or) for easy remembrance use L = A . W

This law is very important to check whether the load testing tool is not a bottleneck.
For Example, in a shop , if there are always 2 customers available at the counter queue , wherein the customers are entering the shop at the rate of 4 per second , then time taken for the customers to leave from the shop can be calculated as

N = X. R
R = 2/4 = 0.5 seconds

A Simple example of how to use this law to know how many virtual users licenses are required:

Web system that has peak user load per hour = 2000 users
Expected Response time per transaction = 4 seconds
The peak page hits/sec = 80 hits/sec

For carrying out Performance tests for the above web system, we need to calculate how many number of Virtual user licenses we need to purchase.

N = X . R
N = 80 . 4 = 320

Therefore 320 virtual user licenses are enough to carry out the Load Test.

Enable remote desktop connection from remote registry

Machine A : PC which you are using to active remote desktop connection in another PC

Machine B : PC for which remote desktop connection has to be activated.

Step 1: From Machine A : Goto Start -> Run -> regedit. Open the Registry window of Machine A.

(Note: User ID logged in Machine A should have ADMIN rights in Machine B)

Step 2: Click “Connect Network Registry“

Step 3:Enter the computer name of Machine B, for which we have to change the settings and Click “OK”

Step4:The destination machine (Machine B) will be connected with our current logged in machine (Machine A).

Step 5:Goto the below mentioned path and change the fDenyTSConnections to “0” and click “OK”.

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows NT\Terminal Services

Step 6:After doing the following changes, right-click the remote machine (Machine B) name and click Disconnect.

NOTE: If suppose the above mentioned registry value is not found, then create a DWORD parameter with a value ’0′.

How to check vuser status per script in Analysis in Load runner

To check vuser status (i.e. passed/failed/stopped) per script perform the following:

1. Analyse the results in Analysis
2. Open the Vuser Summary graph.
3. Right-click on the graph, select "Set filter," then select the script name.
4. Select the Vuser End Status that you are interested in (Passed/Failed/Error/Stopped).