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Once you have identified your performance goals, your next step is to determine how the system is performing at present. The aspects of a system's performance that you measure depend on the sort of tasks you expect it to carry out. These are some typical criteria that you might use to judge a system:
If the system is meant to perform a single function, or run a particular application or benchmark, then you might only look at specific resources. However, it can still be helpful to acquire a sense of the performance of the entire system. If the goals set for the system involve the tuning of applications, then the tuning information provided with the application should be applied before looking at more general system performance.
To gain an overview of the system's current performance, you should read and use ``Tools reference'' which discusses the various system resources, and how you can monitor these.
You should collect data over a duration that is long enough for you to be able to establish normal patterns of usage. You should not make decisions that may be based on observations of performance anomalies though your goal may be to smooth these out.
If your goal involves improving the performance of a particular application, you must understand the application's use of systems resources if you suspect that it is not performing as well as it should. Tuning information may be available in the documentation provided with the application. If this is not available, then an indication of how the application uses resources can be gained by gathering system information for a period before installing the application, and comparing that information with information gathered while the application is in use.