See Also
If you have deployed only one or two Standard Edition servers and Office Communications Server is not a mission-critical application for your organization, the remove/reinstall migration path is an option worth considering. In this path, you take a server offline, remove the Office Communications Server 2007 software from it, and then install and activate Office Communications Server 2007 R2 on the same computer. You can reuse your existing DNS records and IP addresses, but you will need to export your user data before you remove Office Communications Server 2007 from the server.
For deployments that contain one or more Enterprise pools or in environments where Office Communications Server is mission-critical, we do not recommend remove/reinstall migration. Because you cannot place Office Communications Server 2007 servers in the same pool with servers from the 2007 R2 release, your pool will be offline until all servers in the pool have been upgraded. Additionally, if it becomes necessary to roll the deployment back to the 2007 release, you will have to manually remove Office Communications Server 2007 R2 from each server in the pool and then reinstall Office Communications Server 2007. During the rollback, the pool will again be offline until all servers are running the same version of Office Communications Server.