Migrating to a new CUCM cluster in CTS-Manager is fairly easy and should not impact meetings. All meeting details are pulled from Exchange and stored in each individual room's mailbox. As each room's "Room Name from Exchange" is the same between the old and new CUCM clusters, nothing will happen to the meetings. Even if all the rooms disappear from CTS-Manager, the meetings would stay in those room mailboxes. When the new CUCM is added, CTS-Manager will rediscover all the rooms from the associated Application User. Then it will look at the Room Name from Exchange configured for each of these rooms, sync the meetings back from Exchange for that room, and the meetings will get pushed back out to the phones
1. Install the new CUCM, create the device profiles for your endpoints, and create a new Application User. Link to CUCM documentation for CTM. Double check that each Room Name from Exchange field is exactly the same as on the old cluster. Do not associate the MAC addresses with the Application User yet.
2. Turn off meeting notificatations in CTS-Manager under Application Settings -> Meeting Notification Email -> Enable Feature. If you don't, every meeting organizer might get a new confirmation email for their meeting.
4. Log in to the CTS-Manager web GUI and go to the Unified CM tab. Starting in CTM 1.6, you can add multiple CUCM clusters to a single CTM. Configure the new CUCM cluster with the empty Application User set up in step 1.
5. Migrate the rooms from the old CUCM to the new CUCM.
6. Add the endpoint MAC addresses to the application user on the new CUCM. Remove the MAC addresses from the old user.
7. From the Unified CM tab in CTM, select the old CUCM then click the Discover Rooms. This will empty all the endpoints from the CTM database. Select the new CUCM then click Discover Rooms.
8. Verify the migration went as expected, then turn meeting notification emails back on.
After rediscovering the rooms, it will take a few minutes for each room to become synced and for CTS-Manager to redownload all of the meetings. Check the meetings tab to ensure the meetings have been added back to the CTM database. Check the Microsoft Exchange Web Services tab as well and ensure all rooms are synced and subscribed. If any room is not synced or subscribed (and you are sure it was before), double check the Room Name from Exchange in the CUCM Device Profile.