Last year we upgraded our GIS servers SDE SQL Sever and ArcGIS Server etc. We kept our old SDE server up for a couple months during the transition So the new server had a different name.
Here is the lesson learned. When you shut down the old server everything will seem to be fine until somebody in one of the departments decides they need to look at a MXD from a couple years ago and it had not been updated with the new connections for the new server.
The MXD hangs for ever and will not open at ALL!!!! I figured it would open but give red exclamation marks showing the broken connections.
But they will not ever load. Luckily still had the server and switched it on without it being connected to our SAN (no database) but plugged into the network. The mxd's loaded and we are amble could fix the connections. I have a couple workstations in my office I use for testing so I renamed the workstation to be the same name as the old server and changed the IP address to be the same as old server and then shut down the old server. That works and just takes a little bit longer because of the broken connections. For some reason the problem is not being able to find the server name or IP address..
So, if you are getting ready to replace servers, keep this in mind!!!