Converting BMS maps and using the Map class

A large proportion of existing CICS applications use BMS maps for 3270 screen output.

This means that the server application can use data structures corresponding to named fields in the BMS map rather than handling 3270 data stream directly. The EPI BMS conversion utility uses the information in the BMS map source to generate classes specific to individual maps, that allow fields to be accessed by their names, and allow field lengths and attributes to be known at compile time.
Figure 1. Use of BMS map classes
This diagram shows the use of the BMS map classes in a network diagram. The BMS Mapsets is connected to the BMS Conversion Utility. This Utility is then connected to the CICS Map Classes. In turn these Map Classes are connected to the Client Application and also the CICS EPI Classes. The CICS EPI Classes has 2 additional connections one back to the client application and one to the CICS BMS Application/CICS Server

The utility generates C++ class definitions and implementations that applications can use to access the map data as named fields within a map object. A class is defined for each map, allowing field names and lengths to be known at compile time. The C++ classes use the CICS® EPI base classes to handle the inbound and outbound 3270 data streams. The generated classes inherit a base class CclMap that provides general functions required by all map classes.

Run the CICSBMSC utility on the BMS source as follows:

CICSBMSC <filename>.BMS

See the note at Making EPI calls from a C++ Client program for BMS support on Linux.

The utility generates .HPP and .CPP files containing the definition and implementation of the map classes.

Having used the EPI BMS utility to generate the map class, use the base EPI classes to reach the required 3270 screens in the usual way. Then use the map classes to access fields by their names in the BMS map. The map classes are validated against the data in the current CclScreen object.


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Timestamp icon Last updated: Tuesday, 19 November 2013


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