Oracle Message NNO-00252 - invalid administrative region parameter string value string

ERRORinvalid administrative region parameter string value string
CAUSEThe server encountered an invalid administrative region parameter. This error will prevent the server from starting. The administrative region description is stored in the servers names.ora configuration file.
ACTIONMake sure that the names.admin_region 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.