Use the Query Monitor to measure query executions and cache hits. This can be useful for performance analysis in a complex system.
Enable the Query Monitor in either of these ways:
Set the System property
<property name="eclipselink.profiler" value="QueryMonitor"/>
The monitor dumps the number of query cache hits and executions (misses) once every 100 seconds.
For more information about querying, see Chapter 10, "Understanding Queries."