Have you ever wondered what those FMH messages mean in your Stats?

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The FMH flows are the Connect Protocol that rides on your network whether it is TCP, SNA or UDT.

It is one of the layers of Security built into the Product so that Connect Direct always knows that it is communicating with another Connect Direct Node.

So if a connection request is received and it is not a Connect Direct formated FMH message the connection is dropped immediately and protecting your company.

Here are the basic messages for the FMH's.

If you are the PNODE you send an FMH68.

FMH68 is the first File Management Header (FMH) setting up the C:D BIND to the remote node.

The remote then verifies the NETMAP for your connection request.

They send an FMH70.

FMH70 is the charateristics of the NODE. The PNODE sends the (TYPE - Tandem, UNIX etc.), (ACSII, EBCIDIC), and RUSIZE info.

You acknowledge the FMH70.

You send FMH72.

FHM72 is Security. User ID Password.

They verify the Security whether it is SNODEID or Secure Point of Entry (SPOE) also known as a Proxie.

You send FMH71.

FMH71 is DCB parameters, DSN, DISP etc.

They reply to the FMH71 verifying the DSN, File permissions, allocate file space, DISP etc….

Then DATA flows.

After the acknowledgement to the completion of the STEP. STEP could be COPY, RUN TASK, etc.
 

A FMH7402 is Step Termination. If there is another STEP the Process Script Continues.

Otherwise you reply No More STEPs with an FMH7404. End the Process and they reply.

FMH7404 is Process Termination.

Session Ends with FMH75.

FMH75 is Session Termination.
 

Here is an example where knowing how the FMH's can help you diagnose a problem.

Remember when reading your Stats  you might see as an example - FMH72 expected and not received.

This would indicate you were waiting on the user Security from the remote node but that RU never came. 

So you would check with the remote node to see what problem they had when trying to build and send you the 72.

Or it could be they sent it but you did not receive it due to a network problem.