You can monitor performance statistics by using the Admin Console user interface, the stats-xml URI, and the perfdump. For these monitoring methods, the server uses the statistics it collects. None of these monitoring methods will work if statistics are not collected.
The statistics give you information at the configuration level, the server instance level, or the virtual server level. The statistics are broken up into functional areas.
Java Virtual Machine (JVMTM)
Host DNS Cache
Client DNS Cache
In-Memory File Cache
Session Threads, including profiling data (exists if profiling is enabled)
Some statistics are set to zero if Quality of Service (QoS) is not enabled. For example, the count of open connections, the maximum open connections, the rate of bytes transmitted, and the maximum byte transmission rate is zero if disabled.
To enable statistics, use Admin Console.
Collecting statistics causes a slight hit to performance.