DFS1201I UNABLE TO OPEN {SYSIN| SYSPUNCH|DCTIN|DEFLTS}

Explanation
 The DCB for the SYSIN, SYSPUNCH, DCTIN, or DEFLTS
DD statement cannot be opened. The most probable cause is a missing
DD statement.

System action
 The MFS Service utility processing continues
with a missing SYSIN DD statement. The MFS DCT utility ends with a
return code of 12 when any of the data sets cannot be opened.

Programmer response
 Correct the error, and resubmit the job.