Heap Dump created by JVM is incomplete

Question

I want to analyze the memory usage of the application using eclipse MAT, therefore I'm using -XX:+HeapDumpOnOutOfMemoryError to create a heapdump. Now if I open it in MAT, it tells me that the heap dump has a size of 127mb which is clearly not everything as the jvm is run with -Xmx1024m .

Answer 1

There are usually two segments of memory in the Java VM (the nursery and the heap), each of which can cause OutOfMemory. You therefore cannot conclude, that the size of the dump file should equal or exceed the -Xmx setting.

Read more on the topic - eg here: http://docs.oracle.com/cd/E13150_01/jrockit_jvm/jrockit/geninfo/diagnos/garbage_collect.html