XRF allows an alternate, partially initialized CICS® system to take over control from an active CICS system which has failed. The use of VTAM® persistent sessions provides an alternative to XRF. Persistent sessions allow you to restart a failed CICS in place, without the need for network flows to rebind CICS sessions. (Note that you cannot specify both XRF and CICS persistent session support for the same system.)
XRF provides availability of the system (through active and alternate systems) and availability for the user (through availability of the system and exploitation of backup sessions). Active and alternate pairs of systems require their own versions of some data sets (for example, auxiliary trace and dump data sets).
Persistent session support provides availability of the system (through restart in place of one system) and availability for the end user (through availability of the system and persistent sessions). Only one set of data sets is required. Only one system is required. Persistent session support has the following advantages over XRF:
However, persistent session support does not retain sessions after a VTAM, MVS™, or CEC failure. If you need to ensure rapid restarts after such a failure, you could use XRF rather than persistent sessions.