For input only, you can concatenate two or more sequential or regional data sets (that is, link them so that they are processed as one continuous data set) by omitting the ddname from all but the first of the DD statements that describe them. For example, the following DD statements cause the data sets LIST1, LIST2, and LIST3 to be treated as a single data set for the duration of the job step in which the statements appear:
//GO.LIST DD DSNAME=LIST1,DISP=OLD // DD DSNAME=LIST2,DISP=OLD // DD DSNAME=LIST3,DISP=OLD
When read from a PL/I program, the concatenated data sets need not be on the same volume. You cannot process concatenated data sets backward.