EXEC sp_addlinkedserver
 @server=N' DB_INSTANCE2',
 @srvproduct=N'',
 @provider=N'SQLNCLI',
 @datasrc=N' DB_INSTANCE2DB2';

sp_addlinkedsrvlogin @rmtsrvname = 'DB_INSTANCE2', @useself = 'TRUE'

sp_addlinkedsrvlogin
 @rmtsrvname = 'DB_INSTANCE2',
 @locallogin = 'Local_SQLLogin',
 @rmtuser = 'RemoteSQLLogin',
 @rmtpassword = 'rmtpassword'