When preparing your routines, remember that:

• User-written routines must follow standard linkage conventions and use the required interfaces. COBOL E15 and E35 user exits must use the special interface provided.
• To use an E32 user exit, your invoking program must pass its address to DFSORT in the parameter list.
• To use any other user exit, you must associate your routine with the appropriate user exits using the MODS control statement. See MODS control statement.
• Your invoking program can alternatively pass the address of an E15, E18, E35, and E39 user exit to DFSORT in the parameter list.
• When Blockset or Peerage/Vale is used and your user exits are reenterable, the entire DFSORT program is reenterable.
• If you are using ASCII input, remember that data presented to your user exits at user exits are in EBCDIC format. If the E61 user exit is used to resolve ASCII collating for special alphabetic characters, substituted characters must be in EBCDIC, but the sequencing result depends on the byte value of the ASCII translation for the substituted character.