Below are the screen shots for making the gateway service as single sign-on:
Once application is developed in SEGW, use T-code /IWFND/MAINT_SERVICE for registering the service
Click on “Add Service” button to add/register the service. Below screen will appear once you click on button
Fill all the required fields with service class name and press Enter.
Service name will appear in ‘Select Back-end Services’ section.
Click on service name, one popup will appear as per the below screen shot.
As per the above screen shot, you will find last row as ‘OAuth enablement’. Which will be unchecked by default. Click on check box to make the service available on Single Sign-On.
Above all the steps are to make ODATA service single sign-on.