I often do this to ensure performance on a session where it would take time to re-insert large numbers of 'static data' facts.
// Insert a fact and get a handle on to it
FactHandle handle = mySession.insert(myFact);
// Fire rules
mySession.fireAllRules();
// And retract the fact
mySession.retract(handle);
You may wish to fire all rules again after the retract to bring the session back to its previous state.