Hi neela,
You have to verify that your non sap system was implemented using <a href="http://help.sap.com/saphelp_nw04/helpdata/en/22/04287a488911d189490000e829fbbd/frameset.htm">RFC SDK</a> to connect to SAP.
The on R3 you should create an RFC destination of type TCP/IP, let's say 'THIRD_PARTY_RFC', select <i>'Registered server program'</i> and assign a program ID let's say 'THIRD_PARTY'.
Your third party system then should register itself on sapgateway of R3 (<i>transaction SMGW</i>) with the same program ID 'THIRD_PARTY'. To check that it is logged: <i>SMGW->goto->logged on clients</i> and check if an entry for the program id exists.
When calling the RFC/BAPI from R3 use THIRD_PARTY_RFC as destination.
An that's all!
Hope it helps,
Kind regards,
Sergio
