Hi,
Normally ORA-12545 error occurs, if the client is not able to contact the listener on the specified node (incorrect node address, firewall block acess...)
Could you able to do "tnsping PRD" command successfully? Also try to post oracle "alert_PRD.log" error message, if any, during the issue time.
Also try to use IP address in TNSNAMES.ora file for "HOST" entry if you are using hostname there.
Regards,
Ganesan
Message was edited by: K GANESAN