Monitor Java heap usage

I am about to monitor JVM memory utilization for individual nodes. The tool (JON 3.3) has different metrics like initial heap/non heap , committed heap/non heap , used heap /non heap , maximum heap/non heap usages. I have decided to monitor used heap and committed heap usage to observe the memory performance of JVM.

Is it enough to watch mentioned parameters if not what are the other parameters should be monitored apart from used and committed heap usage.Please advice on this.

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Solution

init

represents the initial amount of memory (in bytes) that the Java virtual machine requests from the operating system for memory management during startup. The Java virtual machine may request additional memory from the operating system and may also release memory to the system over time. The value of init may be undefined.
used

represents the amount of memory currently used (in bytes).
committed

represents the amount of memory (in bytes) that is guaranteed to be available for use by the Java virtual machine. The amount of committed memory may change over time (increase or decrease). The Java virtual machine may release memory to the system and committed could be less than init. committed will always be greater than or equal to used. max represents the maximum amount of memory (in bytes) that can be used for memory management. Its value may be undefined. The maximum amount of memory may change over time if defined. The amount of used and committed memory will always be less than or equal to max if max is defined. A memory allocation may fail if it attempts to increase the used memory such that used > committed even if used <= max would still be true (for example, when the system is low on virtual memory). Below is a picture showing an example of a memory pool:
```
+----------------------------------------------+
+////////////////           |                  +
+////////////////           |                  +
+----------------------------------------------+

|--------|
   init
|---------------|
       used
|---------------------------|
          committed
|----------------------------------------------|
```
Non-Heap memory (~Perm)

Also, the JVM has memory other than the heap, referred to as non-heap memory. It is created at the JVM startup and stores per-class structures such as runtime constant pool, field and method data, and the code for methods and constructors, as well as interned Strings.