Overview of the APPC/VM Assembler Interface

In its simplest form, connectivity is the ability of one program to communicate with another program. In this document, 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.

System 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. z/VM® implements the base set of APPC and several APPC option sets using Advanced Program-to-Program Communication/VM (APPC/VM).

z/VM provides two programming interfaces to APPC/VM:

1. A low-level interface intended for programs written in assembler language. This low-level interface consists of CMS macros and CP macros. In this document we will discuss the APPC/VM macros that are part of the CP programming interface. The CMS macros that you can use with APPC/VM are documented in the z/VM: CMS Macros and Functions Reference and z/VM: CMS Application Development Guide for Assembler.
2. Common Programming Interface (CPI) Communications. This interface (also known as SAA communications interface) can be used with any programming language defined in the System Application Architecture (SAA). For z/VM, this interface can be used in CMS. This interface should be used for new application development.
   Note: For more information about CPI Communications routines, see Common Programming Interface Communications Reference.