How to identify holder of reference to object in Java Memory Analyzer using heap dump

Question

As i have some problems with OutOfMemoryErrors with an application i want to identify the root cause. This i created a heap dump (PHD) from the IBM VM on the AIX server and tried to analyze it using IBM Support assistant 4.1 and its Memory Analyzer tool.

When the heap dump is parsed ISA asks me if i want to run the leak suspect report.

Using the leak respect support i got the information about some classes which consume considerable amount of memory.

What i now want to identify is the holder of the object references, but i can e.g. only see what objects a ArrayList contains, but not who holds a reference to that ArrayList.

How can i get to that information?

Answer 1

Load you heap Dump in Memory Analyzer (MAT).

Go to Histogram and see the big size Object.

Now right click on this and select Immediate dominators. It will open a dominator tree and u can identify what is holding your object.

Sometimes when the big size object is local variable you will not be able to see immediate dominators in tree. It can only tell you that your variable is part of which thread.(Below image doesn't show this local variable scenario)

In that case check (stack trace ) where are you getting OutOfMemoryError. Then accordingly trace it backwards and try to find out in which method are you creating big size objects as local variables. Most of the cases we get big size objects in same method which is shown in stack trace as at some point of time while allocating more memory we get OutOfMemoryError.

More details.