Update documentation for com.ibm.jvm.Dump API

[chandrams]

Dump.setDumpOptions() did not work when I passed the below option:
"java:events=throw,filter=java/lang/NullPointerException#DumpTest.main*,range=1..1"

After investigation, I found -Xdump:dynamic has to be specified if throw/catch events are configured through Dump.setDumpOptions() when JIT is ON, whereas this option is not required when we set the above option on command line using -Xdump

Documentation for com.ibm.jvm.Dump API needs to be updated. Also update the user guide as required.

[chandrams]

@pshipton @keithc-ca

The OpenJ9DiagnosticsMXBean internally uses Dump.setDumpOptions() to dynamically configure dump options and trigger dumps on a remote application. At present we need to specify -Xdump:dynamic during the application startup for dynamically configuring throw/catch events using Dump.setDumpOptions() to work, which is not good as the application has to be restarted and the whole purpose of dynamic configuration is lost.

Can we enable -Xdump:dynamic option by default when JIT is ON and the user specified throw/catch events using Dump.setDumpOptions() ?

#718

[pshipton]

There is a performance penalty for enabling -Xdump:dynamic which is why its not enabled by default. The following hooks are enabled.

J9HOOK_VM_EXCEPTION_THROW
J9HOOK_VM_EXCEPTION_CATCH

[pshipton]

It appears using -Xdump:dynamic disables aot.

   if ((*vmHooks)->J9HookDisable(vmHooks, J9HOOK_VM_EXCEPTION_CATCH) ||
       (*vmHooks)->J9HookDisable(vmHooks, J9HOOK_VM_EXCEPTION_THROW))
      {
      self()->setOption(TR_DisableThrowToGoto);
      doAOT = false;
      }