HP-UX SNAplus2 R7 LUA Programmer's Guide

Concepts
LUs and Sessions
• The Session-Level Interface (SLI) is a higher-level interface, allowing the programmer to work at a logical
message level rather than being concerned with the detail of individual RUs. For example:
• The session can be established and terminated with a single SLI verb (rather than with a sequence of RUI
verbs corresponding to the individual RUs involved in session startup and termination).
• The SLI library controls chaining when the application needs to send or receive data that is longer than the
maximum RU length specified in the BIND.
• For most SNA commands sent to the host, the SLI library can build the appropriate RU at the request of
the application.
The SLI interface supports SNA Function Management Profiles 3 and 4, and SNA Transmission Services Profiles
3 and 4.
An application can use only one of these interfaces for each session. For example, if it starts a session using the
RUI, it cannot subsequently issue SLI verbs on that session.
You should consider the following points before deciding which API to use.
• The SLI handles some of the detail of individual RUs and their contents, simplifying the processing required in
the application. The RUI requires the application to deal with each RU individually.
• The RUI provides control over the detailed contents of RUs sent to the host, and allows the use of a wide range
of SNA bind profiles. The SLI does not provide the same degree of control or flexibility.
UNIX
• The RUI includes Primary RUI(HP-UX only), which allows you to write an application that acts as an SNA
primary for communications with downstream PUs. The SLI interface does not provide this function.
1.3 LUs and Sessions
Figure 1–1, SNA Components Used for LUA Communications, shows the SNA components used for LUA
communications with a host.
Figure 1–1 SNA Components Used for LUA Communications
LUA
application
LUA LU
Node
Host
application
Host LU
Host
SSCP
LU Session
SSCP Session
PU-SSCP Session
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