A performance test helps you determine whether a multi-client system is performing within user-defined standards under varying loads.
You run performance tests against database servers, TUXEDO servers, and Web servers to find the point at which the system breaks under load or stress.
Performance tests typically involve loading the server with many virtual testers. For example, you might have a timer in one virtual tester to find out how much time a query takes when 1000 other virtual testers are sending requests to the same server at the same time.
Additionally, one or more GUI users can be included in the test to measure a variety of performance issues that occur when many virtual testers are running against the same server. Because GUI users measure client response times, this end-to-end response time is more indicative of what a real user experiences when there is significant client processing or screen-painting time associated with the user activity you are measuring. Also, a GUI user is a good cross-check for your virtual tester responses.