If you want to associate the SORTIN data set with SORTWK01, you can include the parameter UNIT=AFF=SORTIN in the DD statement for SORTWK01. The AFF subparameter causes the system to place the data set on the same unit as the dataset with the ddname following the subparameter (SORTIN, in this case).

In the same way, you can associate the SORTIN data set with the SORTOUT data set or an OUTFIL data set by including UNIT=AFF=SORTIN in the SORTOUT or OUTFIL DD statement.

SORTINnn tape data sets must all be on different tape units because they are read concurrently. SORTOUT and OUTFIL tape data sets must all be on different tape units because they are written concurrently.