Oracle Message NNO-00320 - missing server name parameter

ERRORmissing server name parameter
CAUSEthe server could not find a names.server_name parameter. The name is specified in the servers names.ora configuration file.
ACTIONMake sure that the names.server_name parameter in names.ora is correct. The names.ora file is automatically generated by the Oracle Network Manager, but administrators can edit the file at any time, introducing errors. If the file was never changed, contact Worldwide Customer Support.