Various exemplary embodiments relate to a method performed by a policy and charging rules function (PCRF) node for selecting an Online Charging System (OCS), the method including: receiving a session establishment request for a subscriber (subscriber session); selecting an OCS realm for the subscriber session based on, in order of priority: policy rules, subscriber attribute or system preference; selecting an OCS host for the subscriber session based on, in order of priority: policy rules, subscriber attribute or system preference; and creating an Sy session using the selected OCS realm and selected OCS host.