APPC/VM Assembler Interface

In its simplest form, connectivity is the ability of one program to communicate with another program. In this book, we are concerned with communications between two application programs. Application programs are typically written to communicate with one another because a user needs access to some kind of data.

Systems Network Architecture (SNA) defines various sets of rules for data to be transmitted in a network. Application programs communicate with each other using a layer of SNA called Advanced Program-to-Program Communication (APPC). APPC is also known as LU 6.2. VM implements the base set of APPC and several APPC option sets using Advanced Program-to-Program Communication/VM (APPC/VM).

VM provides two programming interfaces to APPC/VM:

  1. A low-level interface intended for programs written in assembler language.
  2. Common Programming Interface (CPI) Communications (also known as SAA* communications interface).
    Note: Refer to the CPI Communications Reference for more details about CPI Communications routines.
The following communications programming interface is also available in z/VM:
  • The Inter-User Communication Vehicle (IUCV), which is for communications between two programs on the same VM system. IUCV also allows a program to communicate with a CP system service. For complete information on IUCV, see the z/VM: CP Programming Services.