Perfect sense. It's a little technical.
5250 screens showing a list use something called a "subfile".
There are three types of subfiles:
- load all subfile
- expanding subfile
- page at a time subfile
The general user will not be able to tell the difference. You have to
delve into the code to notice a difference.
The exception to the general user rule is if the user tries to roll past
9,999 records. That's the limit on a subfile size. The "page at a time"
subfile takes more coding but doesn't have this limitation.

General programming rule of thumb:
If it's a really small list and will never grow huge (like a list of
states) then a "load all" subfile is ok. Do all the I/O and fill it up.
The user can wait on the I/O for such a small list.
If it could be a long list but less than 9,999 rows then use an expanding
subfile. Only load enough rows to fill a screen. If they roll forward do
more I/O. If they roll back just read from the subfile.
If it could be a long list and likely to go over the 9,999 rows then use
the page at a time subfile. Keep track of where you are at. Clear the
subfile and reload the screen full upon every roll. Forward or back.

Rob Berendt

As an Amazon Associate we earn from qualifying purchases.

This thread ...


Follow On AppleNews
Return to Archive home page | Return to MIDRANGE.COM home page

This mailing list archive is Copyright 1997-2022 by and David Gibbs as a compilation work. Use of the archive is restricted to research of a business or technical nature. Any other uses are prohibited. Full details are available on our policy page. If you have questions about this, please contact [javascript protected email address].

Operating expenses for this site are earned using the Amazon Associate program and Google Adsense.