If you are moving your 3.6 server to another 3.6 server rim has a whitepaper on what they call a knife edge cut over. I used it when I was migrating from one server to another. I searched RIM's support site and found this. Knife Edge Cut Over
It is for a 4.0 server. I know that they have one for a 3.6 because I have used it, I was just not able to find it on there site. You might be able to do a better search than I. Let me know if this helps.