Logical Unit 6.2 is an IBM-originated communications protocol specification dating from 1974, and is part of IBM's

Systems Network Architecture Systems Network Architecture (SNA) is IBM's proprietary networking architecture, created in 1974. It is a complete protocol stack for interconnecting computers and their resources. SNA describes formats and protocols but, in itself, is not a pi ...

(SNA). A device-independent SNA protocol, it is used for peer-to-peer communications between two systems, for example, between a computer and a device (''e.g.'' terminal or printer), or between computers. LU6.2 is used by many of IBM's products, including

Common Programming Interface for Communications Common Programming Interface for Communications (CPI-C) is an application programming interface (API) developed by IBM in 1987 to provide a platform-independent communications interface for the IBM Systems Application Architecture-based network, a ...

Intersystem Communications (CICS ISC), and

Information Management System The IBM Information Management System (IMS) is a joint hierarchical database and information management system that supports transaction processing. History IBM designed the IMS with Rockwell and Caterpillar starting in 1966 for the Apollo pr ...

, and also many non-IBM products. In 1986, Bruce Compton, Manager of Office Systems and Technology with General Electric, said:

LU 6.2 means I don't have to write the software communications interfaces. If I have one office server in a DEC environment, and another in a Wang environment… I can use the LU 6.2 standard to pass files between those devices, and I don't have to worry about things like block checking and clock.

Some examples of non-IBM products which implemented the SNA stack including LU6.2 are:

Microsoft Host Integration Server Microsoft Host Integration Server (a.k.a. HIS) is a gateway application providing connectivity between Microsoft Windows networks and IBM mainframe and IBM i systems. Support is provided for SNA, 3270 (standard and TN3270), 5250 (standard ...

, and

NetWare NetWare is a discontinued computer network operating system developed by Novell, Inc. It initially used cooperative multitasking to run various services on a personal computer, using the IPX network protocol. The original NetWare product in 19 ...

for SAA. APPC is a protocol used with LU6.2 architecture. APPC is often used to refer to the LU6.2 architecture or to specific LU6.2 features. LU6.2-compliant devices operate as peers within the network and can perform multiple simultaneous transactions over the network. LU6.2 devices can also detect and correct errors. The LU6.2 definition provides a common API for communicating with and controlling compliant devices. Although the concepts were the same on all platforms, the actual API implementation often varied on each IBM platform which implemented it. Other vendors also implemented LU6.2 in their own products and with their own APIs. IBM later defined the

(CPIC) API which would eventually become widely implemented. CPIC allowed for the authoring of multi-platform code. Adoption was slow but steady. As of November 1987, of 207 large US companies interviewed "Eighteen percent of the companies said they have implemented LU 6.2 systems already, and 51% said they expect to have such systems up and running within two years."

References

{{Reflist LU6.2 Network protocols LU6.2