You can write a routine to alter control fields before DFSORT compares them. This allows you, for example, to normalize floating-point control fields. It also allows you to modify the order in which the records are finally sorted or merged, a function for which you would usually use DFSORT's ALTSEQ program control statement. You must associate this routine with the E61 user exit.

When an E61 user exit is used, the subsequent comparisons always arrange the modified control fields in ascending order.