DFSORT places the address of a parameter list in general register 1. The list begins on a fullword boundary and is three fullwords long. The parameter list for the E61 user exit is as follows:

The control field length allows you to write a more generalized modification routine.

To alter the control field, change the control field image at the indicated address (changing the address itself will have no effect).

 SORT FIELDS=(4,2,CH,A,8,10,CH,E,25,2,BI,E)

For all fields except binary, the total number of bytes DFSORT passes to your routine is equal to the length specified in the m parameter of the SORT or MERGE statement.

All binary fields passed to your routine contain a whole number of bytes; all bytes that contain any bits of the control field are passed. If the control field is longer than 256 bytes, DFSORT splits it into fields of 256 bytes each and passes them one at a time to your routine.

Your routine cannot physically change the length of the control field. If you must increase the length for collating purposes, you must previously specify that length in the m parameter of the SORT or MERGE statement. If you must shorten the control field, you must pad it to the specified length before returning it to DFSORT. Your routine must return the field to DFSORT with the same number of bytes that it contained when your routine was entered.

When user exit E61 is used, records are always ordered into ascending sequence. If you need some other sequence, you can modify the fields further; for example, if after carrying out your planned modification for a binary control field, and before handing back control to DFSORT, you reverse all bits, the field is, in effect, collated in descending order as illustrated by the E61 example in Figure 1.

Note that if E61 is used to resolve ASCII collating for special alphabetic characters, substituted characters must be in EBCDIC, but the sequencing depends upon the byte value of the ASCII translation for the substituted character.