Difference between Concurrent & Simultaneous users in Performance Testing.

Understanding the difference between the Concurrent and Simultaneous users is very much important in generating the type of user load for performance testing.

Concurrent users:

Concurrent users are connected to your test application and are all requesting work at some time intervals but not all at once and not for the same thing (same request or page).

In loadrunner concurrency between the user transactions can be achieved by introducing randomized think time (lr_think_time) and the end of transactions.

Example:

• Below is the table of 5 users working in an e-commerce application.
• We could see that each user is in a different transaction denoted by x mark.
• Transactions highlighted in Green are completed by the user and in yellow are yet to be started which also differs from user to user.

Simultaneous users:

Simultaneous users are connected to your test application and who are all requesting work at the same time and for the same thing (same request or page).

In loadrunner simultaneous user can be achieved by using lr_rendezvous function above the transaction for which we need a simultaneous hit to the server or by selecting all user simultaneously in the controller during the load test.

Example:

• Below is the table of 5 users working in an e-commerce application.
• We could see that all the users are in the same search cart transaction denoted by x mark.
• Transactions highlighted in Green are completed by the user and in yellow are yet to be started which also remains the same for all users.