I wanted to know how can we implement the Page up and Page down logic in a PL/1 program .
I am trying to display data's in an online screen . The data's are present in an IMS table . If the no of records retrived is more than the maximum number if lines that can be displayed in the screen , then we need to enable the page down logic so that by pressing a key we can display the remaining records .
In DB2 , we use cursor to implement the same . Similarly do we have any logic in PL/I - IMS programming to implement the same .
You cannot be sure exactly how many times you need to page down, and it would be wasteful of I/O to prepare for the maximum number of browse forward.
Say if your screen displays 24 segments of IMS, then always read the first 24 records and populate the screen. At the same time read the next 24 segments and store in a TSQ. If the user come back DFHAID=PF8, then populate the screen with 24 TSQ records, then read ahead to the next 24 segments, in readiness for the user's next PF8 without waiting. If the user then develops an appetite for PF7 backwards, then more work at more cost will be needed.