As a follow-up, I restarted HornetQ and attempted to move the messages again, this time I received an OutOfMemory Exception. Memory usage went from less than 1/2 a Gigabyte and spiked to 2.5 Gigabytes before the Exception was thrown.
I tried again, and a portion of the messages moved (6508 messages). I've now run moveMessages several more times, and each time it moves 6508 messages.
Ultimately, what is the expected behavior of moveMessages with a large number of messages?