LU 6.2 API Application Programmer's Reference Guide (30294-90008)

22 Chapter1
The SNA Network and LU 6.2 API
Systems Network Architecture (SNA)
Figure 1-3 Logical Mapping of LUs
LU Type 6.2
Logical Unit types are usually used for device emulation. LU.T2 devices
or applications emulate IBM 3270 terminals, and LU.T1 and LU.T3
devices or applications emulate printers. Logical Unit Type 6.2 differs
from other LU types in that it does not emulate a device. LU 6.2
applications exchange raw data in a format called the generalized
data stream. LU 6.2 applications can use the generalized data stream
to exchange unformatted data, binary data, or data formatted for
non-SNA applications and devices.
The LU 6.2 architecture defines two kinds of Type 6.2 LUs: dependent
LUs and independent LUs.
•Adependent LU can communicate only with dependent LUs on a
Type 5 (host) node. It cannot issue a BIND to initiate a session.
When a dependent LU wants a session with the host, it sends an
INIT_SELF request and waits for the host to send the BIND. A
dependent LU can carry on only one session at a time.
•Anindependent LU can communicate directly with an
independent LU on a Type 2.1 (peer) node, like an IBM AS/400. An
independent LU can initiate a session by sending a BIND to the
remote LU, or it can receive a BIND from the remote LU.
An independent LU on the HP 3000 can carry on multiple,
simultaneous (parallel) sessions with independent LUs on remote
systems.Some remote systems, like the IBM AS/400, can perform
intermediate routing between nodes in an SNA network. An
independent LU connected to one of these systems can take
advantage of its routing capabilities to communicate with nodes that
are not directly connected to the HP 3000.
NOTE On MPE XL, Type 6.2 LUs may be configured as independent or
dependent. On MPE V, all Type 6.2 LUs are dependent LUs.