>>-DYNALLOC--,DDN=ddname--+-----------------+------------------->
                          |             (1) |   
                          '-,DSN=dsname-----'   

>--+-------------------------+--+--------------------+---------><
   |        (2)              |  |                (3) |   
   '-,UNIT=------+-/devnum-+-'  '-,VOLSER=serial-----'   
                 +-devnum--+                             
                 '-devtype-'                             

1. Required for data sets.
2. Required for unit record, graphic, and teleprocessing devices.
3. VOLSER is ignored if the UNIT parameter is not present.