Advanced Program-to-Program Communication
Encyclopedia
In computing
, Advanced Program to Program Communication or APPC is a protocol which computer program
s can use to communicate over a network
. APPC is at the application layer
in the OSI model
, it enables communications between programs on different computers, from portables and workstations to midrange and host computers.
APPC was developed as a component of IBM
's Systems Network Architecture
or SNA. Several APIs were developed for programming languages such as COBOL
or REXX
.
APPC software is available for many different IBM and non-IBM operating systems, either as part of the operating system or as a separate software package. APPC serves as a translator between application programs and the network. When an application on your computer passes information to the APPC software, APPC translates the information and passes it to a network interface, such as a LAN adapter card. The information travels across the network to another computer, where the APPC software receives the information from the network interface. APPC translates the information back into its original format and passes it to the corresponding partner application.
APPC is linked with the term LU 6.2 ( Logical unit type 6.2 )
APPC is to a large extent limited to the IBM operating systems such AS/400, OS/2 and AIX. It is still a major part of "mainframe" (ie IBM 360/370/4300 "Z" systems) communications. Microsoft also included SNA support in Microsoft's Host Integration Server
. Major IBM software products have included support for APPC, including CICS
, DB2
, CIM
, WebSphere MQ
and MVS
.
Unlike TCP/IP, in which both communication partners always possess a clear role (one is always server
, and others always the client), the communication partners in APPC are equal, i.e. everyone can be both servers and clients equally. The role, and the number of the parallel sessions between the partners, is negotiated over so-called 'CNOS' sessions (Change Number Of Session) with a special log mode (e.g. at IBM, 'snasvcmg'). Communication of the data is made then by 'data sessions', their log modes can be determined in detail from the VTAM
administrator (e.g. length of the data blocks, coding etc..).
With the wide success of TCP/IP, APPC has declined, although many IBM systems have translators (such as the iSeries' ANYNET) to allow sending APPC-formatted traffic using Ethernet for the physical connection.
Computing
Computing is usually defined as the activity of using and improving computer hardware and software. It is the computer-specific part of information technology...
, Advanced Program to Program Communication or APPC is a protocol which computer program
Computer program
A computer program is a sequence of instructions written to perform a specified task with a computer. A computer requires programs to function, typically executing the program's instructions in a central processor. The program has an executable form that the computer can use directly to execute...
s can use to communicate over a network
Computer network
A computer network, often simply referred to as a network, is a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information....
. APPC is at the application layer
Application layer
The Internet protocol suite and the Open Systems Interconnection model of computer networking each specify a group of protocols and methods identified by the name application layer....
in the OSI model
OSI model
The Open Systems Interconnection model is a product of the Open Systems Interconnection effort at the International Organization for Standardization. It is a prescription of characterizing and standardizing the functions of a communications system in terms of abstraction layers. Similar...
, it enables communications between programs on different computers, from portables and workstations to midrange and host computers.
APPC was developed as a component of IBM
IBM
International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...
's Systems Network Architecture
Systems Network Architecture
Systems Network Architecture is IBM's proprietary networking architecture created in 1974. It is a complete protocol stack for interconnecting computers and their resources. SNA describes the protocol and is, in itself, not actually a program...
or SNA. Several APIs were developed for programming languages such as COBOL
COBOL
COBOL is one of the oldest programming languages. Its name is an acronym for COmmon Business-Oriented Language, defining its primary domain in business, finance, and administrative systems for companies and governments....
or REXX
REXX
REXX is an interpreted programming language that was developed at IBM. It is a structured high-level programming language that was designed to be both easy to learn and easy to read...
.
APPC software is available for many different IBM and non-IBM operating systems, either as part of the operating system or as a separate software package. APPC serves as a translator between application programs and the network. When an application on your computer passes information to the APPC software, APPC translates the information and passes it to a network interface, such as a LAN adapter card. The information travels across the network to another computer, where the APPC software receives the information from the network interface. APPC translates the information back into its original format and passes it to the corresponding partner application.
APPC is linked with the term LU 6.2 ( Logical unit type 6.2 )
APPC is to a large extent limited to the IBM operating systems such AS/400, OS/2 and AIX. It is still a major part of "mainframe" (ie IBM 360/370/4300 "Z" systems) communications. Microsoft also included SNA support in Microsoft's Host Integration Server
Host Integration Server
Microsoft Host Integration Server is a gateway application providing connectivity between Microsoft Windows networks and IBM mainframe and AS/400 systems. Support is provided for SNA, 3270 , 5250 , CICS, APPC, and other IBM protocols...
. Major IBM software products have included support for APPC, including CICS
CICS
Customer Information Control System is a transaction server that runs primarily on IBM mainframe systems under z/OS and z/VSE.CICS is a transaction manager designed for rapid, high-volume online processing. This processing is mostly interactive , but background transactions are possible...
, DB2
IBM DB2
The IBM DB2 Enterprise Server Edition is a relational model database server developed by IBM. It primarily runs on Unix , Linux, IBM i , z/OS and Windows servers. DB2 also powers the different IBM InfoSphere Warehouse editions...
, CIM
CIM
CIM may refer to:Institutions and companies:* California Institution for Men, a state prison in the USA* Canadian Institute of Mining, Metallurgy and Petroleum* Canadian Investment Manager designation of the Canadian Securities Institute...
, WebSphere MQ
WebSphere MQ
IBM WebSphere MQ' is a family of network software products launched by IBM in March 1992. It was previously known as MQSeries, a trademark that IBM rebranded in 2002 to join the suite of WebSphere products. WebSphere MQ, which is often referred to simply as "MQ" by users, is IBM's Message...
and MVS
MVS
Multiple Virtual Storage, more commonly called MVS, was the most commonly used operating system on the System/370 and System/390 IBM mainframe computers...
.
Unlike TCP/IP, in which both communication partners always possess a clear role (one is always server
Client-server
The client–server model of computing is a distributed application that partitions tasks or workloads between the providers of a resource or service, called servers, and service requesters, called clients. Often clients and servers communicate over a computer network on separate hardware, but both...
, and others always the client), the communication partners in APPC are equal, i.e. everyone can be both servers and clients equally. The role, and the number of the parallel sessions between the partners, is negotiated over so-called 'CNOS' sessions (Change Number Of Session) with a special log mode (e.g. at IBM, 'snasvcmg'). Communication of the data is made then by 'data sessions', their log modes can be determined in detail from the VTAM
VTAM
Virtual Telecommunications Access Method is IBM's software package that provides communications via telecommunication devices for mainframe environments. It is the implementation of Systems Network Architecture for mainframes...
administrator (e.g. length of the data blocks, coding etc..).
With the wide success of TCP/IP, APPC has declined, although many IBM systems have translators (such as the iSeries' ANYNET) to allow sending APPC-formatted traffic using Ethernet for the physical connection.