E35 LINKAGE SECTION fields for fixed-length and variable-length records

The fields in the LINKAGE SECTION are used by DFSORT and your routine as stated later in this section. For clarity, the field names from Figure 2 have been used.

To give your COBOL routine the status of the passed records, DFSORT uses the record flags field (RECORD-FLAGS) in the following way:
0 (FIRST-REC)

The record leaving DFSORT is the first passed record.

4 (MIDDLE-REC)

The record leaving DFSORT is not the first passed record.

8 (END-REC)

There is no record leaving DFSORT to pass; all records have been passed to your routine or there were no records to pass.
DFSORT places the next output record, which usually follows the record in the output area, in the record leaving field (LEAVING-REC). A VLR does not contain an RDW; DFSORT places the length of this VLR in the record-leaving length field (LEAVING-REC-LEN). The value in the LEAVING-REC-LEN field is the length of the record only and does not include the 4 bytes for the RDW.
When your routine places an insertion or replacement record in the return record field (RETURN-REC), the VLR must not contain an RDW; your routine must place the length of this record in the return record length field (RETURN-REC-LEN). The value in the RETURN-REC-LEN field is the length of the record only and does not include the 4 bytes for the RDW.
DFSORT places the record already in the output area in the record in output area field (OUTPUT-REC). A VLR does not contain an RDW. DFSORT places the length, not including the 4 bytes for RDW, of this VLR in the record in output area length field (OUTPUT-REC-LEN).
DFSORT passes your COBOL E35 routine a 256-byte user exit area field (EXITAREA) that can contain information passed by your COBOL E15 routine. If no information is passed in the EXITAREA field by your COBOL E15 routine the first time the field is passed to your COBOL E35 routine, EXITAREA contains 256 blanks, and the user exit area length field (EXITAREA-LEN) contains 256.
Any changes you make to the user exit area field or user exit area length field are passed back to your COBOL E35 routine each time it is called by DFSORT.
Note:
1. Do not set the user exit area length field to more than 256 bytes.
2. VLR records have a 4-byte RDW field at the beginning of each record. The maximum record length plus the RDW will be the length defined for the LRECL attribute of your output data set. COBOL programs do not use the RDW and, therefore, the maximum length defined in your COBOL user exit is 4 bytes less than the LRECL value.
3. You need to code only up to the last field your routine actually uses (for example, up to OUTPUT-REC-LEN if you do not use the user exit area).
4. DFSORT uses the specified or defaulted value for L3 in the RECORD statement to determine the length of the records your E35 user exit passes back to DFSORT. For fixed-length records, be sure that each record your E35 user exit changes or inserts has a length that is equal to the specified or defaulted L3 value. For variable-length records, be sure that each record your E35 user exit changes or inserts has a length that is less than or equal to the specified or defaulted L3 value. Unwanted truncation or abends may occur if DFSORT uses the wrong length for the records passed to it by your E35 user exit.
  For details of the L3 value, see RECORD control statement.