Eclipse Memory Analyser

Read the following good reviews on Eclipse Memory Analyser. Looks like it can read both SUN JVM HPROF memory dumps as well as IBM JDK dumps.

http://memoryanalyzer.blogspot.in/2010/01/heap-dump-analysis-with-memory-analyzer.html

http://memoryanalyzer.blogspot.in/2010/02/heap-dump-analysis-with-memory-analyzer.html#more

http://www.eclipse.org/mat/

Some other interesting blogs that would help us resolve OOM errors :)

http://www.rallydev.com/engblog/2011/09/20/outofmemoryerror-fun-with-heap-dump-analysis/

http://www.rallydev.com/engblog/2012/03/16/java-memory-problems-why-is-my-heap-exhausted/

There is also a good article that contains sample code to simulate a Java OOM error and uses the Memory Analyser tool to identify the root cause of the error - http://www.javacodegeeks.com/2012/05/gc-overhead-limit-exceeded-java-heap.html

C heap vs Java heap

Found this interesting discussion on StackOverFlow around C Heap and Java Heap.
A good read and its important to understand that the JVM is also ultimately a C program :)
 
http://stackoverflow.com/questions/78352/what-runs-in-a-c-heap-vs-a-java-heap-in-hp-ux-environment-jvms

What causes memory leaks in Java?

We know that a memory leak can occur in Java applications when object references are unintentionally held onto after the references are no longer needed. Typical examples of these are large collection objects, a unbounded cache, large number of session objects, infinite loops etc. A memory leak results in a OutOfMemoryError.
Besides this core reason, there are other factors that may also result in a OutOfMemoryError exception

1. Java heap fragmentation: Heap fragmentation occurs when no contiguous chunk of free Java heap space is available from which to allocate Java objects. Various causes for this problem exist, including the repeated allocation of large objects (no single large fragment in first generation). In this case, even if we see good amount of free heap, memory allocation fails.

2. Memory leaks in native heap. This problem occurs when a native component, like database connections, is leaking.

3. Perm size has exhausted. The permanent generation of the heap contains class objects. If your code is using a lot of reflection/introspection, then a number of temporary class objects are created that would exhaust the perm space. More info can be found here.