Example: using different input files

This example shows that you use the same COBOL program to access different files by coding a DD statement or an export command before the programs runs.

Consider a COBOL program that contains the following SELECT clause:


SELECT MASTER ASSIGN TO DA-3330-S-MASTERA

Assume the three possible input files are MASTER1, MASTER2, and MASTER3. Before running the program, code one of the following DD statements in the job step that calls for program execution, or issue one of the following export commands from the same shell from which you run the program:


//MASTERA     DD   DSNAME=MY.MASTER1,. . .
export MASTERA=DSN(MY.MASTER1),. . .

//MASTERA     DD   DSNAME=MY.MASTER2,. . .
export MASTERA=DSN(MY.MASTER2),. . .

//MASTERA     DD   DSNAME=MY.MASTER3,. . .
export MASTERA=DSN(MY.MASTER3),. . .

Any reference in the program to MASTER will therefore be a reference to the file that is currently assigned to the ddname or environment-variable name MASTERA.

Notice that in this example, you cannot use the PATH(path) form of the export command to reference a line-sequential file in the z/OS® UNIX file system, because you cannot specify an organization field (S- or AS-) with a line-sequential file.