In the past when we saw there were memory issues that brought down the entire site. We have used a few methods but this was the most effective and helped us figure out the issue. Heap dumps are pretty good but they take a long time and tools have size/JDK/OS limitations to load them.
Application servers > server1 > Process Definition > Java Virtual Machine
Set this parameter in the Generic JVM arguments
The histogram gave a pretty good idea of the objects in memory that helped us trace the issue.