Queues). When a handler
is registered with the Reactor, the Reactor increments the reference count
on the handler. The Reactor also increments this reference count when making
upcalls on the handler. The reference count is decremented when an upcall
completes or when the handler is removed from the Reactor.</li>

<p>This mechanism is similar to what happens between POAs and Servants
and it allows for the safe deletion of handlers. This mechanism is particularly
need for multi-threaded applications that can 