Update releases include fixes to known bugs. This has to finally be the decision of the application maintainer, but if there are fixes to crashes and security issues we believe you will want to have them. Software vendors often state which Java version they have tested with, and therefore which version they support: Sun would encourage software vendors to state that an application requires a specific version of Java, or later.

All utilities which show utilization of system resources are relevant: the process called java still uses CPU, memory, files, etc... in the same way any other process does. A Java application can still perform poorly if it is starved of memory or CPU, just like a native application.

Anything which shows function names or symbols could be misleading, the Class and method names in a JVM are not available as normal symbols - e.g. pstack from core files

The point to remember here is that there are two views of Threads and their stacks: the OS point of view, and the Virtual Machine point of view.

This is solved with for example pstack on Solaris from Java 5 on Solaris 10.

There are also two views of memory usage. There is the memory information reported by the OS, e.g. on Solaris: pmap, and the ps command that shows memory size in various ways (total, resident). Then there is the Java heap, monitored by -verbose:gc and other GC options to the JVM. The Java heap is a subset of the process' total memory consumption, as it also maintans the usual native "C heap" plus the program and libraries themselves. It is useful to have enough physical memory enough to contain the Java heap, for speed of Garbage Collection.

Java is documented heavily on sun.com, java.sun.com, java.net and much of the Internet. Whatever questions remain, there is probably a document about it. The trick is to not be put-off if the documentation appears aimed at developers, programmers, etc...