If you have to rename an existing server running MS SQL-Server is more complicated than you might think. Just renaming the server is not enough.

Especially renaming the running SQL-Server is at first challenging. You cannot just open the properties and do something like “rename”. In order to rename a SQL-Server you have to execute a SQL-Statement:

 USE master
 EXEC sp_dropserver 'old-servername'
 GO
 EXEC sp_addserver 'new-servername', 'LOCAL'
 GO

Especially tricky is, that Microsofts documentation was missing the LOCAL part of the sp_addserver statement.

Link: BUG: “Renaming A Server” Topic in SQL Server Books Online is Incomplete