Is your goal to implement interprocess communications within and potentially among OpenVMS servers using (any) available means, or is your goal specifically involving the use of MPI on OpenVMS?
Examples of available communications options include ICC, 0MQ, networking (UDP, TCP, multicasts, DECnet, etc), shared memory, and a variety of other protocols.
As for MPI on OpenVMS, AFAIK, not so much. It's supposedly portable, and older versions apparently have occasionally been ported to OpenVMS. (No, I don't have any references.)
HP sold off its MPI products a while back, FWIW.
What I have on this topic is posted here and here.
Yes, I know several ways to establish communications between programs you mention.
For example, some time ago I used pthread library under OpenVMS.
However, current goal is to port our parallel code to DS25 server that I got occasionally.
Our code is based on MPI and we would like to avoid code modification and low-level programming.
Our primary code development platform is OpenVMS Alpha where the code runs in single-processor mode, and further exploitation is held on Linux MPP systems.
