Major programming elements in a VTAM application program

Figure 1 shows the major functions that any VTAM® application program performs:

Opening and closing the program (associating the program with and dissociating it from VTAM)
Establishing and terminating sessions with other LUs
Communicating with LUs with which the program is in session.

Figure 1. Major functions of the communication part of a VTAM application program

A diagram that shows the VTAM application program contains processing parts and communication part. The communication part includes the major functions: Opening and closing the program, establishing and terminating sessions with other LUs and communicating with LUs.

Figure 2 and Figure 3 show these major functions in more detail in the approximate order in which the functions occur. Although not every VTAM facility is shown, the facilities that are shown give a general idea of a VTAM application program. (In particular, the application program is the PLU; a different set of macroinstructions and exits is used to establish and terminate a session in which the application program is the SLU.) Following Figure 2 and Figure 3, the numbers beneath the section headings correspond to the numbers in Figure 2 and Figure 3.

Figure 2. Major programming elements in the communication part of a VTAM application program (Part 1 of 2)

A diagram that shows major programming elements in the communication part of a VTAM application program.

Figure 3. Major programming elements in the communication part of a VTAM application program (Part 2 of 2)