User mapping from portal to R/3

Hello everyone,

Our situation is this :

We made some visual composer iviews (charts and tables) that get data from R/3.

Instead of creating users in R/3, we want to use only one public user who can only call RFC's in R/3. So how is the user mapping implemented in this situation?

Please give me detailed explanation for it or links of documentation.

I will be appreciative and all answers will be rewarded with points.

Thanks for help.