Summary of logical unit (LU) types

This chapter describes the logical unit (LU) types that WSim currently supports. It also gives an example of the hardware or software products that typically use each type of logical unit. For more information about these LU types, refer to Systems Network Architecture: Reference Summary.

LU Type 0
LU Type 0 uses SNA-defined protocols for transmission control and data flow control but uses user-defined or implementation-defined protocols to supplement or replace higher-layer protocols. For example, use an LU Type 0 for applications using IMS/VS to communicate with an IBM® 4700 Finance Communication System.
LU Type 1
LU Type 1 is used for communication with single-device or multiple-device data processing workstations in the following environments:
  • Interactive
  • Batch
  • Distributed data processing.
This type of logical unit uses the SNA character string (SCS) or the Document Content Architecture (DCA) data stream. For example, use an LU Type 1 for applications using IMS/VS and communicating with an IBM 8100 Information System.
LU Type 2
An LU Type 2 is for an application that communicates with a single display workstation in an interactive environment. It uses the SNA 3270 data stream. For example, use an LU Type 2 for applications using IMS/VS or CICS/VS and communicating with an IBM 3179 Color Display Station.
LU Type 3
LU Type 3 is used for communication with a single printer. It uses the SNA 3270 data stream. For example, use an LU Type 3 for applications using CICS/VS and sending data to an IBM 3287 Printer attached to an IBM 3274 Control Unit.
LU Type 4
LU Type 4 is used for either of the following:
  • Communication with a single-device or multiple-device data processing or word processing workstation in an interactive, batch, or distributed data processing environment.

    For example, use an LU Type 4 for an application that uses CICS/VS and communicates with an IBM 6670 Information Distributor.

  • Logical units in peripheral nodes that communicate with each other.

    For example, use an LU Type 4 for an IBM 6670 Information Distributor communicating with another 6670.

An LU Type 4 uses SNA character strings (SCS) for data processing environments and Office Information Interchange (OII) Level 2 for word processing environments.
LU Type 6.1
LU Type 6.1 is used for an application subsystem that communicates with another application subsystem in a distributed data processing environment. For example, use an LU Type 6.1 for an application program using CICS/VS to communicate with an application program using IMS/VS.
LU Type 6.2
LU Type 6.2 is used for an application that communicates with another application in a distributed data processing environment. It uses either of the following data streams:
  • SNA general data stream (GDS)
  • User-defined data stream.
LU Type 6.2 sessions provide communication between two Type 5 nodes, a Type 5 node and a Type 2.1 node, or two Type 2.1 nodes. Examples of an LU Type 6.2 include the following:
  • An application that uses CICS/VS and communicates with another application program that uses CICS/VS
  • A CPI-C client transaction program that runs on a workstation and communicates with a CPI-C server running on a CICS/VS host system
  • An application in a System/38 that communicates with an application in a System/36.
LU Type 7
An LU Type 7 is for an application that communicates with a single display workstation in an interactive environment. It uses the 5250 data stream. An example of this type of logical unit is an application running on a System/34 that communicates with an IBM 5251 Display Station.
Below illustrates which LU types can be used with different types of simulations.
Simulation Types LU Types
VTAMAPPL All
SNA All