Information DFSORT passes to your routine at E15 user exit

Your E15 user exit routine is entered each time a new record is brought into the input phase. DFSORT passes two fields to your routine each time it is entered:

The address of the new record. End of input is reached when there are no more records to pass to your E15 user exit; DFSORT indicates end of input by setting this address to zero before entering your E15 user exit. If there are no records in the input data set (or no input data set), this address is zero the first time your E15 is entered.
After end of input is reached, DFSORT continues to enter your user exit routine until you pass back a return code of 8.

Your E15 user exit must not change the address of the new record.
The user exit address constant. If you invoked DFSORT with a user exit address constant in the parameter list, the address constant is passed to your E15 user exit the first time it is entered. This address constant can be changed by your E15 user exit any time it is entered; the address constant is passed along on subsequent entries to your E15 user exit and also on the first entry to your E35 user exit. For example, you can obtain a dynamic storage area, use it in your E15 user exit, and pass its address to your E35 user exit.

Note: The user exit address constant must not be used for a tape work data set sort application.