This metric can affect overall performance of the underlying OS, if the JVM consumes all available memory.

Heap memory usageis the amount of memory that the JVM allocates for objects used by the running Java system.

Unused objects are regularly removed from the heap by the garbage collector.

Non-Heap memory usageis the amount of memory allocated to the method area and the code cache.

The method area is used to store references to loaded classes.

It can also indicate a thread-creation leak.

This can give you an idea of how much memory your tool consumes without the JVM overhead.

Threadsis the number of active threads in the JVM.

Classesis the number of loaded classes.

ReadJava Virtual Machine: the Essential Guideto learn the basics of JVMs.