If you have been handed a .phd file which is a dump of the heap of an IBM Java virtual machine, you can analyse it using the Eclipse Memory Analyzer Tool (MAT), but you must install the IBM Monitoring and Diagnostic Tools first.
Download MAT from eclipse.org/mat/downloads.php. I suggest the Standalone version.
Unzip it and run the MemoryAnalyzer executable inside the zip. Add an argument to control how much memory it gets e.g. to give it 4GB:
./MemoryAnalyzer -vmargs -Xmx4g
Once it’s started, go to Help -> Install new software.
Next to “Work with” paste in the URL for the IBM Developer Toolkit update site: http://public.dhe.ibm.com/ibmdl/export/pub/software/websphere/runtimes/tools/dtfj/
Type in a name like “IBM Monitoring and Diagnostic Tools” and click OK.
In the list below, an item should appear called IBM Monitoring and Diagnostic Tools. Tick the box next to it, click Next, and follow the wizard to accept the license agreements and install the toolkit.
Restart Eclipse when prompted.
Choose File -> Open Heap Dump and choose your .phd file. It should open in MAT and allow you to figure out who is using all that memory.