Defining a program operator

A VTAM® application program can be authorized to issue VTAM operator commands to:
  • Display the status of the network
  • Control the status of the network
  • Receive messages from VTAM
  • Reply to VTAM messages.
Such an application program is called a program operator, or a program operator application (POA), and permits a user to:
  • Enter operator commands from any LU in the network (for example, from a terminal)
  • Monitor and control elements in the network at program execution speed
  • Specialize network control by dividing the network among several application programs
  • Define specialized commands (for example, to display the status of the entire network with a single command)
  • Reformat replies received for VTAM commands (for example, to reformat the status display of a part of the network to fit on a 3270 display screen)
  • Coordinate control of different domains in a multiple-domain network.
A program operator can:
  • Issue a DISPLAY, MODIFY, or VARY command by using a SENDCMD macroinstruction. The format of the command is the same as though it were issued from the system console.
  • Receive messages from VTAM by using a RCVCMD macroinstruction.
  • Reply to a VTAM message by using a SENDCMD macroinstruction to send a REPLY command.

Figure 1 shows how the system console operator and a program operator send VTAM operator commands and receive VTAM operator messages to control the VTAM domain. OPNDST, SEND, RECEIVE, and CLSDST are examples of session-establishment and communication macroinstructions.

Figure 1. VTAM operator control of a VTAM domain
The diagram shows how a VTAM operator controls a VTAM domain. The VTAM operator commands and the VTAM operator messages are sent through a host processor.

The NetView® program provides many of the facilities listed in the preceding section while also providing a base for communication network management functions.

In a multiple-domain network, program operators in different domains can communicate by means of VTAM macroinstructions to allow a program operator or an operator at a terminal to monitor and control elements in other domains. Figure 2 shows an example of how a multiple-domain network can be controlled using two program operators.

Figure 2. VTAM operator control of a multiple-domain VTAM network
The diagram shows how a VTAM operator controls a VTAM domain. The VTAM operator commands and the VTAM operator messages are sent through a host processor.

To activate an element in domain 2:

  1. An operator at a terminal in domain 1 sends a command to program operator 1.
  2. Program operator 1 determines that the command is for domain 2 and sends it to program operator 2.
  3. Program operator 2 sends the command to VTAM (using a SENDCMD macroinstruction), where the command is processed.
  4. Program operator 2 sends any replies back to program operator 1, which, in turn, sends them to the terminal.

Another way to activate an element in domain 2 is to have a terminal establish a session directly with program operator 2.

Two levels of authorization for an application program determine the type of messages that the program can receive. A program can be authorized to:
  • Receive only messages that are in reply to VTAM operator commands issued by a program operator (solicited messages). Such an application program is called a secondary program operator (SPO).
  • Receive messages whether they are in reply to VTAM operator commands that the program operator issued (solicited messages) or are as a result of unexpected events in the network (unsolicited messages), for example, losing contact with a terminal. Such an application program is called a primary program operator (PPO).

Only one primary program operator can be active at a time; however, one or more secondary program operators can also be active.

Note: If a primary program operator is active, the systems' operations console does not receive unsolicited messages.