Connect PowerNet 3270, Справочное руководство

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February 1998 4-1
4 Dialog Language Objects
Introduction
Small installations can easily use the
Quick Start
features of the PowerNet 3270
Connectivity Package. Larger sites can benefit greatly from the more robust
scripting capabilities that are included.
Dialog scripts are created using the system editor and the Dialog Language.
Scripts reduce the impact of inherent differences between genuine, full screen
terminals and handheld units. Although the entire host display area and keyboard
are processed using both the
Quick Start
and scripting methods, there are two
primary reasons for using the script facility—performance and operational
simplicity.
The performance of the server is optimized by maintaining a block-oriented, half-
duplex flip/flop environment when using
Dialog Language Scripts
. Block-oriented
is a term indicating that each exchange consists of a single unit of information.
Half-duplex flip/flop describes a network relationship in which the two partners
alternate between transmit and receive states.
In contrast, the
Quick Start
environment is a full-duplex contention environment.
The communicating partners are always ready to receive and may transmit
simultaneously. Radio, being a multiple access network media, does not lend itself
well to this kind of environment, due to the transmit collisions. When traffic is low,
the collisions are infrequent, but as traffic increases, so do collisions, which affect
network performance.
The Dialog Language Script allows the server, rather than the terminal, to deal
with the logon screens and unsolicited host updates without involving the radio
network. Also, this task is removed from the operator’s responsibilities list.
3270 Session Overview
Developing a dialog script for 3270 sessions requires some familiarity with the
behavior and terminology associated with 3270 Hosts and terminal networks. The
presentation space (PS) is the 24 by 80 character display area of the 3270
terminal. A 3270 PS may be field formatted, in which case data is entered into
unprotected fields. The Dialog Language provides for program controlled data
entry into both the formatted and unformatted PS and allows for field addressing
within the formatted PS.