JVMPI_GC_ROOT_MONITOR_USED - what does this mean in a heap dump?

Question

I'm having some OutOfMemory errors in my application, so I turned on a profiler, and took a heap dump before and after an operation that is blowing up the memory.
What changes after the operation is that I get an enormous amount of data that is reported under the node JVMPI_GC_ROOT_MONITOR_USED. This includes some Oracle PreparedStatements which are holding a lot of data.
I tried researching the meaning of JVMPI_GC_ROOT_MONITOR_USED, but found little help. Should this be objects that are ready for garbage collection? If so, they are not being garbage collected, but I'm getting OutOfMemoryError instead (I thought the JVM was supposed to guarantee GC would be run before OutOfMemory occurred).
Any help on how to interpret what it means for objects to be reported under JVMPI_GC_ROOT_MONITOR_USED and any ways to eliminate those objects, will be greatly appreciated!
Thanks

Answer 1

I tried researching the meaning of
JVMPI_GC_ROOT_MONITOR_USED, but found little help.
Should this be objects that are ready for garbage
collection? Disclaimer: I haven't written code to use JVMPI, so anything here is speculation.
However, after reading this: http://java.sun.com/j2se/1.4.2/docs/guide/jvmpi/jvmpi.html
It appears that the "ROOT" flags in a level-2 dump are used with objects that are considered a "root reference" for GC (those references that are undeniably alive). Most descriptions of "roots" are static class members and variables in a stack frame. My interpretation of this doc is that objects used in a synchonize() statement are also considered roots, at least for the life of the synchronized block (makes a lot of sense when you think about it).