Before I upgrade a production TFS environment, I always try do to a test migration. This gives us the opportunity to detect possible issues as soon as possible and give some people the change to test the new environment before we do the real migration.
What you need to be aware of when doing this is that TFS uses a set of internal GUIDs. The server has a GUID, the collections have GUIDs and even Team Projects have GUIDs.This means that when you do a migration your new TFS environment will use the same GUIDs out-of-the-box. This is nice because when a user connects to another server with the same GUIDs Visual Studio will automatically transfer all of the user’s cache and workspaces to the new server. This makes an upgrade really convenient and transparent for the user.
So this is perfect for the ‘real’ migration, but for the ‘test’ migration it’s a problem. Because the moment any user tries to connect to the new environment, he gets into trouble when trying to connect to the old environment again(causing some really strange behavior).
To solve this problem you can use the ChangeServerID command:
TFSConfig ChangeServerID /SQLInstance:ServerName] /DatabaseName:ConfigurationDatabaseName [/ProjectCollectionsOnly] [/ConfigDBOnly] [/usesqlalwayson]
However it’s very important that you run this command BEFORE configuring your application tier. If you run it afterwards, you get the following warning:
The command ChangeServerId should only be run against a set of Team Foundation Server databases that have no application tiers configured. Do you want to continue with this operation? (Yes/No)
If you type Yes the command will still be executed but TFS is no longer available. So please really read your warnings
In case this happens to you, the following command will bring rescue:
TFSConfig RegisterDB /SQLInstance:ServerName [/usesqlalwayson]
More information about this issue can be found here: http://nakedalm.com/guide-to-changeserverid-says-mostly-harmless/