Hi Sury,
Please check the tnsnames.ora and listener.ora with matrix below:
TNSNAMES.ORA init*.ora LISTENER.ORA
SERVICE_NAME SERVICE_NAMES GLOBAL_DBNAME
SID/ORACLE_SID INSTANCE_NAME SID_NAME
Please note SAP <sid>adm user will first find the environment TNS_ADMIN to find tnsnames.ora, then goes to oracle directory to find the tnsnames.ora. So you have to verify the tns_admin environment variables.
Best regards,
James
