Calling Java from RPG: more confused than ever about local references and object groups

Scott Klement said (in my "quick questions" thread):

The object group cleans up everything /except/ the 'rsmd' object. You
still need to clean that up when you're done. (Unless there's an
additional begin/end object group that's taking care of it.)

You can refer to it throughout your program after it has been retrieved
-- UNTIL it gets cleaned up (for example, by ending the object group
it's a part of, or freeing that particular object directly, etc.)

I'm looking at jdbc_begin_object_group in the JDBCR4 source. And it looks like every time jdbc_begin_object_group gets called, it, in itself, creates a local reference to the JNI, that never gets explicitly freed up. Now, I trust Scott's knowledge of calling Java from RPG implicitly, but I'm having trouble wrapping my mind around some of the concepts involved.

It's looking like object groups nest. Am I at least getting that part right?

Is my answer then to begin an object group of my own, before I start opening the JDBC connection, and end it as soon as I've closed the connection?

And what happens to any un-freed Java objects when the activation group in which the RPG program runs ends? When the job ends?

--
JHHL