🚀 go-pugleaf

I don't really know why I bother, but anyway:

In article <118@tardis.dbaccess.com> peter@dbaccess.com (Peter A. Castro) writes:
>    As I recall, IUCV is the improved version of VMCF, where VMCF has
>    all the SVC functions for Inter-Machine communication, but needs direct
>    coding by the programmer.  IUCV, on the other hand, has support for Cross-
>    Machine support, being able to send/receive messages between connected
>    machines.  I also remember that both use the same Virtual Machine message
>    operations and tend to conflict with each other, because each requires
>    different interrupt parameters which the Virtual Machine uses to invoke
>    the interrupt routine.  I might suggest that you switch to IUCV, being it
>    is more used by 370 applications for message communication, and in
>    addition, can receive/send messages to other machines.

IUCV is not a superset of VMCF, in particular it does not allow communication
between 2 arbitrary virtual machines without directory authorization. Neither
VMCF nor IUCV uses SVC, although you may of course build a VMCF or IUCV
library which the application programs would invoke via some SVC. Being an
uneducated nerd I have no idea what "indirect coding" is so I cannot comment
on that. IUCV support for cross-machine communication comes with PVM release 4
and is not documented. I guess IBM wants you to use APPC/VM and TSAF for that
purpose, or of course SNA. My lack of education shows again in my inability to
understand the meaning of "Virtual Machine message operation", and I'm afraid
I am yet to see a virtual machine setting up parameters to invoke their
interrupt routines.

Anyway the original poster's problem is that both IUCV and VMCF generate
external interrupts which, obviously, have to be trapped in some way by the
application program. You can do that with HNDIUCV or HNDEXT, or you can do
PSW stealing, and you may or may not code your routine to pass unrecognized
external interrupts back to the routine that was in the external new PSW
before you altered it. Code that is written properly often dies or ignores
unexpected interrupts, which would explain the problem. There is nothing
preventing the use of both VMCF and IUCV in the same virtual machine.

  Eric