Ask the user.
There is no supplied method to determine anything about which pages of a load-all subfile have been viewed. The system doesn’t keep track of the series of page views, and your program receives no information about what the user is doing until the <Enter> or other AID-generating key is pressed.
That’s part of the purpose of a load-all subfile. All of the work of page navigation is handled outside of your program. If you need to know that each page has been viewed, then use either page-at-a-time or extendable subfiles.
Technically, I suppose you <i>could</i> do something like enabling STRCPYSCN to an *OUTFILE and then process the outfile to see if every page is captured… but that seems to be a long way to go when the other two subfile types are available.
if you know the number of records that are loaded, and the number of records that are displayed, you could count the number of times the PAGE/ROLL key is pressed.
this can give you the number of records displayed the terminal, but it can’t guarantee that the user actually looks at them.