HP -UX SNAplus2 Administration Manual page 34

SNA Terms and Concepts
Basic SNA Concepts
For example, LU 3 can support an application program
running under Customer Information Control System
(CICS) and sending data to an IBM 3262 printer
attached to an IBM 3174 Establishment Controller.
LU 2 (for 3270 displays)
LU 2 supports application programs and display
workstations communicating in an interactive
environment using the SNA 3270 data stream. Type 2
LUs also use the SNA 3270 data stream for file
transfer.
For example, the LU 2 protocol can support 3270
emulation programs, which enable workstations to
perform the functions of IBM 3270-family terminals. In
addition, LU 2 is used by other programs to
communicate with host applications that normally
provide output to 3270 display devices. Such TPs
enable the workstation to achieve a form of cooperative
processing with the host.
LU 1 (for 3270 printing and RJE)
LU 1 supports application programs and single- or
multiple-device data processing workstations
communicating in an interactive, batch-data transfer,
or distributed data processing environment. The data
streams used by LU type 1 conform to the SNA
character string or Document Content Architecture
(DCA).
For example, LU type 1 can support an application
program running under Information Management
System/Virtual Storage (IMS/VS) and communicating
with an IBM 8100 Information System. This enables a
workstation operator to correct a database that the
application program maintains.
Applications that use LU 1 are often described as
remote job entry (RJE) applications.
LU 0 (for LUA)
LU 0, an early LU definition, supports primitive
program-to-program communication. Certain host
database systems, such as IMS/VS (Information
Management System/Virtual Storage) and some
point-of-sale systems for the retail and banking
industries (such as the IBM 4680 Store System
34 Chapter 1