Changing the TCAM configuration and MCP to support the BSC link to the SyncDongle

 OVERVIEW OF CHANGES NEEDED

The TCAM message control program (MCP) that will be used by TSO needs to be built to reference remote 3270s connected via a 2703 control unit. The MCP startup procedure needs to specify the address of the 2703 in addition to the local 3270 devices. Finally, Hercules must define the 2703 and invoke the BSC socket at a given port number. 

The system I just generated had entries to define several 2703 communications controllers thus the OS already will support this. I chose to use device x604, the same one selected by Mattis Lind in his project.

POINTING HERCULES AT THE 2703

All that is needed is an entry in the mvs.cnf configuration file used by Hercules to define my virtual data center where I will IPL MVS. The existing configuration file doesn't define the 2703 devices but I need to add one at x604 so that TCAM can try to reach the remote 3174 controller using BSC protocol. 

0604    2703    lport=32701 lnctl=BSC dial=IN

The line above tells Hercules to emulate a 2703 at address x604, using the BSC capability, opening a TCP socket at port 32701 which will be connected to by socat, a tool similar to netcat but taking serial in one side and bidirectionally transferring messages to a TCP destination on the other side. The serial side of socat is connected to my SyncDongle, which has the 3174 cable hooked to its other end. 

BUILDING A TCAM MCP

Creating a TCAM message control program is a two stage process. High level macros are created by the system programmer to define the terminals and other features needed. When these are assembled they produce a stage two jobstream that assembles data areas and hooks them together (link edits) with existing TCAM modules to create our MCP. 

SET UP A START PROCEDURE FOR OUR MCP

In order to bring up TSO, we have to start our MCP. A procedure is installed on the system to start this code and point it at our communications controller at address x604. This procedure is invoked as a command by the operator to start up TSO. This MCP will only handle the remote terminals, so I plan to make adjustments to add in the local 3270 terminals. 

TEST IPL OF MVS WITH THESE CHANGES

I had first tested IPLing the system with the 2703 added but without the MCP set up. It was in fact listening on 32701 for our connection. I used a telnet program to connect just to see what will be emitted, but the BSC code didn't like what it saw and dropped the call. I then used netcat as suggested by Mattis and did see the poll attempts:

7@@@@-7@@@@-7@@@@-7@@@@-7@@@@-

When I broke the network connection the console was flooded with intervention required messages, quickly flooding the WTO (write to operator) buffers. The system was uncontrollable at this point so I tried shutting down things in the blind and then dropped Hercules. 

NEXT STEPS

I want my TCAM MCP to handle both local and remote terminals, thus I have a bit of work to do enabling this. 

It will be time to hook up the SyncDongle and attempt to make this all work. Before that step, however, I need to get a socat equivalent utility installed as that must establish a flow of messages between the async serial port of SyncDongle and the network port 32701 in Hercules that is the 2703 comm controller.