You get the following error message when trying to register the Operations Manager Data Source against the Service Manager Data Warehouse:
Error: Data source registration failed. User does not have permission to perform this action. User or role '<userName>' does not exist in this database. Cannot alter the role '<userName>', because it does not exist or you do not have permission.
This can occur if the console or PowerShell user doing the registration does not have system administrator permissions on the Operations Manager database.
To resolve this issue, provide system administrator permissions on the Operations Manager database for the account being used to register the Operations Manager Data Source.