Rational Developer for System z

General information about Basic Mapping Support (BMS)

Basic Mapping Support (BMS) is an application programming interface between CICS® programs and terminal devices.

For many applications, BMS has several advantages:

The physical map contains the information BMS needs to:
BMS Maps are defined using assembler macros. For example for each field on the screen, you need one DFHMDF macro which looks like this:
Figure 1. DFHMDF macro
fldname DFHMDF  POS=(line,column),LENGTH=number,
                INITIAL='text',OCCURS=number,
                ATTRB=(attr1,attr2,...)

After all the fields in the maps are defined, they are grouped into a single map using the DFHMDI macro. Maps can then be grouped into map sets using the DFHMSD macro.

The second assembly produces a COBOL structure that is known as the symbolic description map (application data structure). This structure defines all of the fields (the ones that you might read or write in your program), so that you can refer to them by name.

The screen definition contains the formatting information, including the number of fields on the screen and the row and column positions of all fields on the screen.

When interacting with a CICS application, the screen description that you capture and save to the workbench is similar in detail to the application screen's Basic Mapping Support (BMS) on the host. The majority of CICS transactions rely upon a component within CICS referred to as BMS to interact with a 3270 terminal. When a transaction calls BMS, it specifies the name of a 3270 screen "map" and a set of fields and values to be used with it. The map determines where on the screen the fields are to be placed and BMS generates the resulting 3270 data stream.

In their final form, the screen descriptions are used along with the screen operations file to provide a service definition for accessing the 3270 application.


Feedback