gtps2m0lACF/SNA Data Communications Reference

TPF Applications

In TPF terminology, an application is defined as a collection of programs is a software package. When a TPF/SNA network is defined, a logical unit is associated with each application. Each LU has a unique network address and network name. TPF requires a node control block (NCB) to control the functions of each LU.

You must define all TPF applications, which are also known as local applications, using the offline ACF/SNA table generation (OSTG) program. The TPF system associates a scratchpad area (SPA) control record with each application that is defined using the OSTG program. This SPA is for the exclusive use of the application.

Non-SNA devices require different control records: the routing control block (RCB) and the agent assembly area (AAA). TPF provides an interface program that converts non-SNA address formats for applications written before the advent of SNA. Applications that are SNA-oriented are called NCB/SPA dependent. Applications that are not SNA-oriented are called RCB/AAA dependent. The discussion throughout this publication pertains to NCB/SPA dependent programs unless otherwise stated.

In the network, TPF applications are viewed as primary logical units. However, a user may optionally request that an application also appear as a secondary logical unit. Here, the application assumes a primary LU status when communicating with an SLU; a secondary LU status when communicating with a PLU. As a secondary LU (also known as an SLU THREAD), the communication rate among applications is limited to the communication rate of the session protocol supported. To ease this limitation, TPF allows the user to specify a number of communication paths (threads) when communicating with a primary LU. Each path (thread) is assigned a unique network address and network name. See TPF ACF/SNA Network Generation for information describing the ANT deck and application SLU threads.

Another way of overcoming this limitation is to use parallel sessions provided with TPF/APPC. See TPF Advanced Program-to-Program Communications for additional information about TPF/APPC.