Adding table rows dynamically during table display scrolling
Assume that you have access to a large amount of related data that might be built into a single table. However, you need to interface with only a subset of that data during an ISPF session, but you are not sure just how extensive that subset is. Normally, you would have to initially construct a table that included all possible data that you might wish to access during a session before you began scrolling and update activity on the table. This could lead to a great deal of unnecessary overhead because you might include a lot of data in your table that you never access.
By interacting with a set of function system variables, an ISPF function can dynamically expand the table as you scroll through it during a session. The function can specify that the table is to be expanded upward when the user has scrolled past the top, expanded downward when the user has scrolled past the bottom, or both. In this way, the function adds only the table rows that satisfy your needs as you need them.