What does it do?
IBM mainframes have a communications arrangement that includes a front end processor (FEP) called a communications controller, which controls and regulates communications traffic with the CPU, particularly remote (modem-attached) traffic and network traffic. In addition, these systems use a device known as a cluster controller, which allows the attachment of multiple 3270 class devices. This cluster controller can be attached to the communications controller, or can be channel-attached directly to the CPU. Cluster controller model numbers include 3174 and 3274.

Within the context of PC integration, a PC can emulate a 3270-class terminal through the addition of a 3270 interface card, which provides the physical coaxial connection, and associated emulation software, which provides the protocol support necessary to establish sessions and communicate with the mainframe.

In addition, it is possible to connect a PC LAN to an IBM mainframe using a 3270 gateway. With this arrangement, PCs on the LAN can act as 3270 terminals without a direct cable connection, since the gateway provides that link.

How is it used?
3270 emulation is a fairly common requirement for PCs and PC LANs in large corporate environments. Since many of an organizations mission-critical, and compute-intensive applications may be handled by IBM mainframes, users need access to these systems, and may need to integrate and process data on their PC that originates from them.

3270 emulation programs frequently offer greater functionality than a dumb terminal, since they may offer multiple, simultaneous sessions with different hosts, and may operate in windows that can be displayed together, or switched to the foreground as necessary. These programs may also facilitate the exchange of files and data between the host system and the PC. Emulation products are available for DOS, Macintosh and Windows platforms.

Where do I get more information?
Contact your local CBV Office.