How do I set up user accesses?

I would like to know which users have access to particular transactions. Is this possible?

Yes. There are several ways. I think the easiest one is for you to run transaction /nSUIM. In this transaction (User Information System), drill down to: Infosystem authorization -User -Users by complex selection criteria -By transaction authorizations Finally, enter the transaction in question and execute. If you are running R/3 4.7, you can also run transaction /nPFCG.