Communications Access Methods for SAS/CONNECT and SAS/SHARE Software

Types of Communications Access Methods

There are two types of communications access methods: program-to-program and terminal-based.

Program-to-Program Communications

Program-to-program communications access methods use networking protocols to allow two processes to interact over a network. They have these advantages over terminal-based communications access methods:

much larger packet sizes
data transmitted in binary form (therefore, not requiring the application to perform any character set encoding)
message notification often performed asynchronously.

Program-to-program communications access methods may require additional system software to achieve support on all of the necessary platforms. Here is a list of program-to-program methods of communication that are supported by SAS/CONNECT and SAS/SHARE.

APPC

is an abbreviation for Advanced Program-to-Program Communication. This type of connection uses the LU 6.2 protocol for distributed processing within an IBM SNA network. APPC and LU 6.2 are often used interchangeably.

CPIC (Version 6 Only)

is an acronym for Common Programming Interface for Communications. This interface supports the IBM SAA (System Application Architecture) solution by providing a method for developing portable distributed applications. CPIC functions as a layer that resides on top of the APPC protocol.

CAUTION:: Version 6 Only The CPIC access method is not supported in Version 7 and later releases. However, information about this access method is included here for Version 6 users.

DECnet

is an acronym for the Digital Equipment Corporation Networking architecture. In SAS documentation, this term describes the task-to-task communication interface over a DECnet network.

NetBIOS

is an acronym for the IBM Network Basic Input/Output System. This is an operating system interface for application programs that are running on nodes in a local area network.

SPX (Version 6 Only)

is an abbreviation for the Novell Sequenced Packet Exchange. This is a communications protocol that provides guaranteed delivery of Internetwork Packet Exchange (IPX) packets. IPX enables NetWare workstations to communicate with NetWare servers, and SPX adds the connection-oriented features required for reliable client/server communication.

CAUTION:: Version 6 Only The SPX access method is not supported in Version 7 or later releases. However, information about this access method is included here for Version 6 users.

TCP/IP

is an abbreviation for Transmission Control Protocol/Internet Protocol. This is a program-to-program interface that is supported by multiple vendors over multiple vendors' hardware.

The following program-to-program-based connection types are supported by SAS/SHARE only:

IUCV

is an abbreviation for Inter-User Communications Vehicle. This interface is a part of the VM/CMS operating system and is used by programs that run under VM/CMS.

VTAM LU 0 (Version 6 Only)

is an acronym for Virtual Telecommunications Access Method. This type of connection uses LU 0 protocol for program-to-program communications with an IBM SNA network under the OS/390 operating system.

CAUTION:: Version 6 Only The VTAM LU 0 access method is not supported in Version 7 or later releases. However, information about this access method is included here for Version 6 users.

XMS

is an abbreviation for Cross-Memory Services. This interface is part of the OS/390 operating system and is used by programs that run within a single OS/390 environment.

Terminal-Based Communications

Terminal-based communications access methods let two processes interact over a network by using a terminal interface. They have these characteristics:

limited transmission packet size (because of the size of the terminal screen)
limited efficiency (because they force the application to perform character-set encoding to write data to the screen even though users are not expected to read from the screen)
message notification generally accomplished through polling.

Because of the limitations of terminal-based communication methods, these methods cannot support Remote Library Services. Terminal-based interfaces, however, are relatively inexpensive and generally available.

The following terminal-based connection types are supported by SAS/CONNECT only:

EHLLAPI

is an acronym for Extended High-Level Language Applications Programming Interface. EHLLAPI is a standard 3270 programming interface that uses the SNA LU2 protocol and is provided by many third-party vendors for OS/2 and Windows workstations. SAS/CONNECT first moved to this standard interface with Release 6.06 of SAS Software under OS/2. EHLLAPI, HLLAPI, and WinHLLAPI are sometimes used interchangeably. Support for Windows HLLAPI (WinHLLAPI) was added with Release 6.11 of SAS software under Windows. Release 6.11 defines a standard and consistent IBM EHLLAPI-style implementation with the addition of Windows specific extensions.

TELNET (Version 6 Only)

is a terminal application interface written to use the TELNET protocol. TELNET is less efficient than TCP/IP because it is layered on top of the TCP/IP protocol. Because TELNET can communicate with an asynchronous interface in the remote environment, and it can run over an existing TCP/IP network, it is useful with SAS/CONNECT when the remote host does not have a supported TCP/IP product.

CAUTION:: Version 6 Only The TELNET access method is not supported in Version 7 or later releases. However, information about this access method is included here for Version 6 users.

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