I have a COBOL DB2 program which extracts data for reporting purpose from different tables and loads data (Use BMC load) into a report table.
The tables(fields) from which data extracted sometimes can be null and the same null value needs to be loaded into the report table . So I have used
null indicators in my output record to capture values for all nullable fields in the report table .
I have used PIC S9(4) USAGE COMP to handle all the null indicator valuesin the output file .
If it looks like this, you should "handle all the null indicator values in the output file" as a PIC x(1) in which you would move HIGH-VALUES when null and LOW-VALUES when not null and place indicators before the column (=pos 29).
the difference 488 - 513 is probably that you defined 25 null indicators as
PIC s9(4) comp (=2 bytes) and a normal unload file uses PIC X (= 1 byte).