External File Mapper (Mfextmap)

You can assign filenames externally using the External File Mapper (Mfextmap). This provides a flexible method of mapping the assigned filename used in your COBOL program to a physical filename, by enabling filename mapping to be resolved in a text file (the mapper file). Filename mappings can be altered subsequently, simply by editing the file.

select filename
   assign to external assigned-name

where the parameters are:

The logical (internal) filename used by your program.
An entry in the mapper file.

Using the External File Mapper, rather than resolving filename assignments via operating system environment variables, reduces the amount of memory required for environment space.