As stated above, system performance monitoring is normally done in response to a performance problem. Either the system is running too slowly, or programs (and sometimes even the entire system) fail to run at all. In either case, performance monitoring is normally done as the first and last steps of a three-step process:
Monitoring to identify the nature and scope of the resource shortages that are causing the performance problems
The data produced from monitoring is analyzed and a course of action (normally performance tuning and/or the procurement of additional hardware) is taken to resolve the problem
Monitoring to ensure that the performance problem has been resolved
Because of this, performance monitoring tends to be relatively short-lived in duration and more detailed in scope.
System performance monitoring is often an iterative process, with these steps being repeated several times to arrive at the best possible system performance. The primary reason for this is that system resources and their utilization tend to be highly interrelated, meaning that often the elimination of one resource bottleneck uncovers another one.