🚀 go-pugleaf

In a recent article CMH117@PSUVM.BITNET (Charles Hannum) writes:
>
>  Exactly what *are* Channel-To-Channel Adapters (CTCAs), and what do
>  they (and CP COUPLE) do?
>
The CTCA is usually used to provide a dedicated, high-speed (typically
3 megabyte/sec) data path between mainframes.  The CTCA itself (which
can be either a feature on the processor or a stand-alone device)
appears to be an I/O device to each processor attached to it.  At the
hardware level, that's all it is...in effect, a very expensive (but very
fast) null modem cable.

In VM you can create virtual CTCA ports with the CP DEFINE CTCA [as] cuu
command; you then use the CP COUPLE command to say what is attached
to the other end of the virtual cable by giving the userid and virtual
address of the distant end.  For example, if A and B want to communicate
over a virtual CTCA, then:

A issues the command:      CP DEFINE CTCA AS 333

B issues the commands:     CP DEFINE CTCA AS 444
                           CP COUPLE 444 TO A 333

and now A and B have a CTCA between them.

What you do with the link is up to your programming system.  It could be
used for data transfer, for supervisory data transfer (e.g., passing
ENQ/DEQ commands between processors which share DASD), or whatever you want.

Hope this helps...

Joe Morris