TfsConfig registerDB /sqlInstance: /databaseName: /usesqlalwayson Changes the database the application tier uses. The sqlInstance ...

TfsConfig   registerDB  /sqlInstance: 
                        /databaseName:
                       [/usesqlalwayson]
    
            Changes the database the application tier uses. 
            The sqlInstance is required and can be of the 
            form  or \.  
            The databaseName is required.

            The UseSqlAlwaysOn option should be used if your databases are
            on a Sql Server High Availability AlwaysOn Availability Group.  
            This option sets MultiSubnetFailover in the connection string.