Hello Phani,
Once you add the new fields in the structure HROVIS_S_NODE_GENERIC, you need to import those newly added fields inside the Entity of your GW model. Once this is done regenerate the run-time objects.
I assume no need to change/enhance the MPC/MPC_EXT class here as the structure HROVIS_S_NODE_GENERIC having your new fields would have already been bound to the MPC.
This you can check if above structure binding is there inside MPC.
Now you can add extra code inside appropriate method in DPC_EXT to populate values into those newly added fields.
Use table /IWBEP/I_SBD_GA to find the project associated to the service name.
Pass your service name to the field 'NAME' and get the project name.
Open this project in SEGW. Not all the services would have been developed using SEGW. Few are developed manually by inheriting the classes as well. You need to check this.
Regards,
Ashwin