This user exit can be used only in a merge operation invoked from a program and cannot be specified on the MODS statement. When an E32 user exit is activated, it must supply all input to the merge. DFSORT ignores SORTINnn data sets when an E32 user exit is used.

You must indicate the number of input files you want to merge using either (1) the FILES=n option on the MERGE control statement, or (2) the X'04' entry in the 24-bit parameter list. Your E32 user exit routine must insert records for these files as DFSORT requests them.

If input is variable-length records, you must be sure the beginning of each record contains a 4-byte RDW before merged. The format of an RDW is described in z/OS DFSMS Macro Instructions for Data Sets (Alternatively, you can declare the records as fixed-length and pad them to the maximum length.)

See Figure 1 for logic flow details.