SNA Link/iX Node Managers Guide (30291-90507)

104 Chapter4
SNA Node Startup and Shutdown
Establishing Sessions with the Remote System
Establishing Sessions with the Remote System
Remote system session establishment is slightly different for a type 2.0
(T2.0) node than for a type 2.1 (T2.1) node. Session establishment for
each node type is explained below, and examples of session
establishment activities between the HP e3000 and the IBM remote
system are shown later in this chapter.
NOTE When configuring a data communications subsystem on the HP e3000,
the node manager can choose to display link, node, and session
activation and termination status messages on the system console. SNA
Transport will then display node activation, link activation, and session
establishment messages as each activity is performed.
These messages are not shown in the session establishment and
termination examples later in this chapter; however, you should be
aware that SNA Transport will keep you informed of activity on the
communications link if you configure this type of logging. More
information about logging can be found in Chapter 5 , “SNA Link
Troubleshooting.”
For a Type 2.0 Node
The System Services Control Point (SSCP) uses PU-SSCP sessions to
control the PU in each node in its domain. Each PU, in turn, controls
the resources of the node it resides in. These resources include the links
which have been configured for the particular node. The SSCP
transmits an ACTivate Physical Unit (ACTPU) command request to the
PU to establish a session with the PU. When a PU-SSCP session is
activated, the node that contains that PU becomes an active node in the
SNA network. SNA Transport manages the PU-SSCP sessions of the
HP e3000.
The SSCP uses LU-SSCP sessions to control dependent LUs and to
establish dependent LU-LU sessions. The SSCP sends the command
ACTivate Logical Unit (ACTLU) to establish LU-SSCP sessions. SNA
Transport manages LU-SSCP sessions on the HP e3000.
A dependent LU-LU session enables data to be exchanged between two
end users, between an end user and an application running on the host
processor (such as TSO), or between a job and the Job Entry Subsystem
(for example, JES2) running on the host. The LU-LU session can be
thought of as a temporary logical connection that allows two LUs to
exchange data.
LUs on the HP e3000 communicate with the SSCP to establish
dependent LU-LU sessions. A dependent LU sends a session initiation
request to the SSCP via its LU-SSCP session. The SNA services