Can you please confirm if the TNS_ADMIN, ORACLE_HOME environment variables are already set in this environment? If not ,can you please set the same and re-run the job.
Set TNS_ADMIN to the path where the tnsnames.ora file is located and ORACLE_HOME where Oracle is installed.
Please verify the details mentioned by Jyoti, Also check whether the Connection string which you are using is proper. verify the entry in the tnsnames.ora file.