I saw this:
6. You will notice that some data items in data division are crossed out. That is because they are not referenced directly in procedure division. Be careful though. Don't be tempted to remove these data items from your code without being sure. If the data item is inside a copy file, then other program may be using them.
But it did not tell me how to disable it. -- Maybe I should just leave there as it is.
Anyway , thank you for the hyperlink.