Limiting the amount of trace data collected

There are two ways to use the trace facility efficiently:

• The trace facility can be turned on and off in multiple ways to capture system activity. It is practical to capture in this way seconds to minutes of system activity for post processing. This is enough time to characterize major application transactions or interesting sections of a long task.
• The trace facility can be configured to direct the event stream to standard output. This allows a real-time process to connect to the event stream and provide data reduction as the events are recorded, thereby creating long-term monitoring capability. A logical extension for specialized instrumentation is to direct the data stream to an auxiliary device that can either store massive amounts of data or provide dynamic data reduction. This technique is used by the performance tools tprof, pprof, netpmon, and filemon.