Joined: 23 Nov 2006 Posts: 19270 Location: Inside the Matrix
Hello and welcome to the forum,
When posting a question it is rather important to post in the correct part of the forum. . .
I suspect the question has nothing to do with db2, so it has been moved to the COBOL part of the forum.
A subject of "COBOL" will get few replies. One needs to use a proper subject. . .
At the top of the page is a link to "IBM Manuals". The first of these is for COBOL. Read about reference modification in one of the Language Reference manuals and if you find something that is not clear, post what you found and your doubt. Someone will be able to clarify.
You might also consider the forum SEARCH (in the blue bar above) as there have been several topics about reference modification.