PHYSICAL AND SYMBOLIC MAPS - IBM Mainframe

Physical maps are primarily used by CICS and their main objective is to ensure device independence in the application programs. They are assembly language programs, which are created and placed in the CICS load library (LOADLIB). They control the screen alignment and sending and receiving of constants and data to and from a terminal. They are coded using BMS macros, assembled and link-edited into the CICS load library as shown in the following figure.

Creation of Physical Maps

Creation of Physical Maps

The Symbolic map is for the use of the application program and its main objective is to ensure device and format independence to the application programs. Symbolic maps define the map fields used to store the variable data referenced in the COBOL program. They can be placed in a copy library and included in the program using a COBOL COPY statement. Therefore through the use of symbolic maps the layout change of the screen does not affect the application program as long as the field names are not changed. A symbolic map also is coded using the BMS macros, assembled and placed in a copy library and will be copied to the application program during compilation. The process is shown in the following figure.

Creation and Use of Symbolic Maps

Creation and Use of Symbolic Maps

As shown in the above figure, the symbolic map will be copied into the application program. The symbolic map starts with the 01 level definition of map name defined in the DFHMDF macro (described later) with the suffix T for input map and 'O' for the output map. Next a filler of PIC X(12) , which is the TIOA prefix, is created if the option TIOAPFX=YES is specified in the DFHMSD macro. For each field name in the DFHMDF macro, BMS creates 3 fields for input and another 3 fields for output by placing a character suffix to the original field name. The meanings of these fields are shown in the below table.

meanings of these fields are shown

For example, after assembling the mapset (say MSET) and map (say MNME) and fields (say FLD1 and FLD2) using the map definition macros the copy library will contain the following copy book:

copy library will contain the following copy book


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