1 User logging in 100 times? or 100 Users logging in only once?

Peter Dhondt has an interesting answer for the oft asked question . This is on the Loadrunner yahoogroups.

This is on the subject of 200 Vusers and the same/different user id's for your test.

It really doesn't matter if the same user can log into the application multiple times or not unless you want to use the same user ID and password for all of your users. But before you can answer that you need to find out a few things.

Typically you would want to use different user id and passwords for your test and here's why:

When a user logs into an application a memory space is created on the backend for that user. Lets call it a workspace for that user. Most applications will share the same workspace if the same user is logged into the application more than once. Here is where your problem is....If the same user is logged into the application 200 times then that user is typically sharing one piece of memory but if 200 users are logged into the application then there will be 200 different workspaces each with their own chunk of memory.

Now in some ERP applications (SAP, Oracle NCA, Peoplesoft)it treats each login as totally separate users and will spawn 2 memory spaces for John being logged in twice. So in that case if your application treats each user login as separate and does not share memory then you can use the same user id 200 times and it would be a legit test. But when you login with 200 (John Smiths) and you have system errors you might be asked which user got the error...Well John Smith did...and you have 200 of them logged into the application at the same time which can be difficult to figure out which user had the problem.

Hence going back to the...."You should have 200 different user IDs".

1. Can you log in multiple times?
2. If you log in multiple times does the system treat it as separate logins or does it share the workspace because it is the same user?
3. If it shares memory I would suggest NOT using the same user ID multiple times.
4. If it treats them as totally separate users then you CAN use the same ID 200 times as long as you understand that error analysis can be very difficult because you can't determine who did what because they all have the same ID's.

5. To be safe and sure you would be better off in the long run getting or creating 200 different user id for this test.