Creating External Services for SAP Transactions 
Use
You create an External Service for an R/3 transaction based on a master iView. For R/3 transactions, however, you do not have to know which master iView is involved because the master iView is selected automatically.
Procedure
To create an External Service of type R/3 transaction:
The External Service is generated based on the master iView.
You now see the finished External Service and can see which properties it has. If necessary, you can overwrite certain properties of the master iView.
Result
You created an External Service for an R/3 transaction that you can insert directly in a role. Read also
Changing External Services in the Role.