Client programs running in an MVS™ address space can communicate only with CICS® server regions running under Version 4 of CICS for MVS/ESA, or a later release.
Also, the client program can connect to the server CICS region only through the Version 4 of CICS for MVS/ESA (or later) level of the interregion communication program, DFHIRP.
For information about DFHIRP, and its requirement to be installed in the MVS extended link pack area (ELPA), see the CICS Transaction Server for z/OS® Installation Guide.
When you use RRMS to coordinate DPL requests, the server CICS region must be running CICS TS Release 3 or later.