In some installations, monitoring of performance activity is done on a demand basis. When a performance problem is reported, the performance analyst runs one or more commands in an attempt to determine why the problem occurred. In some cases, explicit recreation of the problem is needed in order to collect analysis data. The result is that users experience every performance problem twice. It is usually more effective to monitor performance continuously, preferably with automatic collection of additional data if performance deteriorates.
Monitoring can collect data when a problem occurs for the first time.
The following sections discuss several approaches to continuous monitoring. These approaches are not mutually exclusive, but use of more than one may involve some redundancy.