Oracle Message TNS-12203 - TNS: unable to connect to destination

ERRORTNS: unable to connect to destination
CAUSEInvalid address specified or destination is not listening. This error can also occur because of underlying network or network transport problems.
ACTIONVerify that the net service name you entered was correct. Verify that the ADDRESS portion of the connect descriptor which corresponds to the net service name is correct. Ensure that the destination process (for example the listener) is running at the remote node.

445029ORA-12203 composite SAP note
131561Work processes sometimes abend during database connect