Hi, Mike,
In the case of VM/370, you could use VMCF to communicate between virtual machines.?
For MVS, look here:
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/g/INTERCOMM?
Page down below the nice data center picture to read about INTERCOMM, a CICS-like transaction processing system that was popular in the 1970s to early this century.? INTERCOMM had its own equivalent of CICS "MRO" (Multi-Region Option).? We have the source code for all of INTERCOMM, so you could possibly study that code to see how they did it.
The "classic" way this was done, that I recall from the late 1970s, (on MVS 3.7), was that an APF authorized program that could run in supervisor state, key zero (via MODESET) and could then issue a SCHEDULE macro to schedule an "SRB" (service request block) to run in another address space.??
So, for example, you might issue a GETMAIN in CSA, then copy the data you want to send into that buffer, then schedule an SRB into the target address space, and the SRB could then notify the application there to go and look in that CSA buffer, where it can copy the data from.? ?Typically an SRB would POST an ECB in the target address space via a branch entry to POST. (SRBs are meant to be short run-to-completion tasks, so just have an SRB notify some other program already running in TCB mode in the target address space to actually do all the "work."
In later releases of MVS, MVS/SE and MVS/SP and above, you have options such as "cross-memory POST" (XMPOST) that uses the SRBs under the covers for you.? ? You need to know the ASID (address space ID) of the target address space.
If you search the CBT tapes at CBTtape.org you may find several examples of using such cross-memory techniques.? So, if you look at this page:
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and search for "cross memory" on that page, you can find some promising material to study further.
Also on the CBTtape.org web site, you can find copies of many issues of the old XEPHON magazines -- for MVS, see:
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They have some articles about cross-memory services, as well, for example:
Cross memory mapping 159.49-57
Cross memory services 129.27-64
Cross memory services 219.63-71, 220.19-25
I hope that helps,
Mark S. Waterbury
