The conventional Logical Unit Application (LUA) programming interface is an application programming interface (API) that allows you to write LUA applications to communicate with host applications.
The interface is provided at the request/response unit and session levels, allowing programmable control over the Systems Network Architecture (SNA) messages sent between your communications software and the host. It can be used to communicate with any of the logical unit types 0, 1, 2, or 3 at the host; the application must send the appropriate SNA messages as required by the host.
For example, you can use LUA to write a 3270 emulation program that communicates with a host 3270 application.