PU type 2.1
The PU type 2.1 is the physical unit type that is required for an LU 6.2 (see LU
type description following). Examples of PU type 2.1 is an IBM 3820, IBM 3935, or
PSF/2.
Summary of LU Types and Representative IBM Products
Listed below are the LU types that SNA currently defines and the kind of
configuration or application that each type represents. Also mentioned are
hardware or software products that typically use each type of logical unit. A logical
unit (LU) describes the type of relationship that the Host VTAM and applications
have with a specific device such as a printer. This relationship determines the
commands supported from the host to the device and the type of feedback the
device gives to the host.
LU type 0
LU type 0 printers are Non-SNA Local or Bisync connections. This mode is also
commonly called DSC (Data Stream Compatibility) mode printing. An example of
an LU 0 printer connection is an IBM 3816 attached to a non-SNA 3174 control
unit. Not all printers support this type connection. This connection type is used
when VTAM is controlling the non-SNA control unit and device.
LU type 1
An LU type 1 is for an application program that communicates with single or
multiple-device data processing workstations in an interactive, batch data transfer,
or distributed data processing environment. The data stream conforms to the SNA
Character String (SCS) or Document Content Architecture (DCA). Examples of
printers that are able to communicate via LU1 are 4230, 4234, 3930, 6500–v and
others.
LU type 1 is the basic logical unit type for SCS, IPDS, and AFPDS (PSF) printing.
The type of connection is determined by the application that will be driving the
printer. The selection is made by changes in the VTAM logmode entry that is used
for the logical unit. See the examples for the type of connection desired.
LU type 2
LU type 2 is use by an application program that communicates with a single
display workstation in an interactive environment, using the SNA 3270 data
stream. Type 2 LU’s also use the SNA 3270 data stream for file transfer. An
example of an LU type 2 device is a 3270 display such as a 3278, 3178, and others.
Appendix D. Attaching Host Systems to a Coax/Twinax Printer 285
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