HP-UX SNAplus2 R7 APPC Programmer's Guide

Concepts
What Is APPC?
1 Concepts
This chapter introduces the fundamental concepts of advanced program-to-program communication (APPC) in a
distributed processing environment:
• What is APPC?
• A simple mapped conversation
• Confirmation processing
• Sending and receiving status with data
• Conversation states
• Changing conversation states
• Synchronous and asynchronous APPC calls
• Receiving data asynchronously
UNIX
• Syncpoint support
• APPC and CPI-C (Common Programming Interface for Communications)
• TP Server API
1.1 What Is APPC?
APPC stands for Advanced Program-to-Program Communication, an application program interface (API) that enables
peer-to-peer communications among programs in a Systems Network Architecture (SNA) environment.
Through APPC, application programs distributed across a network can work together, communicating with each
other and exchanging data to accomplish a single processing task such as the following:
• Querying a remote database
• Copying a remote file
• Sending or receiving electronic mail
A complete sequence of communications between two application programs, which can accomplish one or more
processing tasks, is referred to as a conversation.
Two communicating APPC applications can be on the same computer or on two separate computers; an application
does not need to know where its partner application is located. An APPC application can run either on a server or
on a client computer.
1.1.1 Transaction Programs
A transaction is a processing task accomplished by programs using APPC. Consequently, programs that use APPC
are called transaction programs (TPs). These programs communicate as peers, on an equal (rather than a hierarchical)
basis. Application TPs accomplish tasks for end users. Service TPs provide services to other programs.
Together, TPs distributed across a local- or wide-area network perform distributed transaction processing.
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