HP-UX SNAplus2 R7 LUA Programmer's Guide

Concepts

Choosing Which Interface to Use

1 Concepts

This chapter introduces the fundamental concepts of LUA—the Conventional LU (Logical Unit) Application

Programming Interface (API).

The topics covered in this chapter are as follows:

• What is LUA?

• Choosing which interface to use (RUI or SLI)

• LUs and sessions

• LUA verbs

• A sample LUA communication sequence

• LUA compatibility

1.1 What Is LUA?

LUA (the Conventional LU Application Programming Interface) is an API that enables you to write SNAplus2

applications to communicate with host applications.

The LUA interface is provided at the request/response unit (RU) level, allowing the programmer control over the

Systems Network Architecture (SNA) messages sent between SNAplus2 and the host. It can be used to communicate

with any of the LU types 0, 1, 2, or 3 at the host; it is up to the application to send the appropriate SNA messages

as required by the host application.

For example, you can use LUA to write a 3270 emulation program that communicates with a host 3270 application;

a simple version of this is included as a sample LUA application with SNAplus2, and described in Chapter 6,

Sample LUA Application.

UNIX

If your SNAplus2 system supports PU Concentration for communications with downstream PUs, you can also write

an LUA application that acts as the SNA primary for communications with secondary LUs on these downstream

PUs. This allows you to emulate a host application on the SNAplus2 node, or to ofﬂoad processing from a host

application to the SNAplus2 node. This function is described as “Primary RUI”; it is speciﬁc to SNAplus2 and

may not be provided by other LUA implementations.

1.2 Choosing Which Interface to Use

LUA includes two different programming interfaces at different levels:

• The Request Unit Interface (RUI) is provided at the request/response unit (RU) level, allowing the programmer

control over the Systems Network Architecture (SNA) messages sent between SNAplus2 and the host. It is up

to the application to build and send the appropriate SNA messages as required by the host application.

The RUI interface supports SNA Function Management Proﬁles 2, 3, 4, 7, and 18, and SNA Transmission

Services Proﬁles 2, 3, 4, and 7.