How do I calculate the number of concurrent users needed for a load test based on the named users for the app?
Question: I am planning to do a load test using Mercury load runner but need to know how many virtual users I will need to simulate the true number of concurrent connections required. I therefore need to calcualte the number of concurrent connections to the web server that are likely from a given user base. for example 100 concurrent users will simulate 1000 active users from a user base of 100000.
I am sure there must be a calculation used that includes think-times and takes account of abandoment etc.
Answer:
you need to specify what type of web server you're running and what admin tools you use
In days of old, with Transaction Processing Systems, the user was required to define peak period transactions per second from a given number of users, and range of transaction types. Tests were often run via a Remote Terminal Emulator connected to the System Under Test via real lines. The overall load was controlled via a random think time, taking into account typing and output times. In most cases, using fewer users working harder was unacceptable. Then there way the other key factor of performance criteria, such as 95% of response times should be less than 3 seconds.
Then, along came a range of UNIX based systems using Relational Database Management Systems with some much heavier transactions for such as searching and report writing. The latter used such a high proportion of system resources that measurement of the impact of these became far more useful than running multiple user benchmarks.
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