Step 4:
Set Objectives for the Performance Study

All performance studies answer one or both of two fundamental questions:

Does the product meet its performance requirements?
Which design option has the best performance?

As in previous steps, these questions are often stated at a business level and must be refined into unambiguous requirements or questions. For example, at the business level, a question might be: "does the proposed cell phone base station set up all calls quickly enough, even during busy hours?" could be translated to "During a busy hour, as defined in the standard workload, are at least 99.5 percent of calls are fully set up within one second after the customer presses the SEND button."

For performance studies that compare multiple design options, both the options and performance objectives must be fully specified. For example, a study of a cell phone base station might include the question:

"For the busy hour standard workload, what are the CPU utilization and call setup latency for input polling intervals of 5, 10, and 20 milliseconds?"

As in previous steps, the major role of the performance analyst is to facilitate setting objectives. The analyst must use his or her knowledge of performance modeling and measurements to suggest performance questions that both support the project's objective and are readily modeled or measured.