Storing data through webservice in PI custom table

Dear All,

In my PI application large number of webservice messages are coming from thirdparty  vandors .As the consumer strength is increasing there is a chance of overload in ISU server.As in PI there is enough space,so to reduce the load in ISU i am thinking of storing the payment details coming from external resources in a custom table in PI server.Is it possible to do so? If yes then how can i do this writing a RFC or proxy in PI.If any alternative please suggest.

Thanks& Regards,
Sonalika