Importance of setting objectives

Although you can set objectives in terms of measurable quantities, the actual desired result is often subjective, such as satisfactory response time. Further, the analyst must resist the temptation to tune what is measurable rather than what is important. If no system-provided measurement corresponds to the desired improvement, that measurement must be devised.

The most valuable aspect of quantifying the objectives is not selecting numbers to be achieved, but making a public decision about the relative importance of (usually) multiple objectives. Unless these priorities are set in advance, and understood by everyone concerned, the analyst cannot make trade-off decisions without incessant consultation. The analyst is also apt to be surprised by the reaction of users or management to aspects of performance that have been ignored. If the support and use of the system crosses organizational boundaries, you might need a written service-level agreement between the providers and the users to ensure that there is a clear common understanding of the performance objectives and priorities.