Library /sys$common/syshlp/pca$help.hlb SELECT, Qualifiers, /SCROLL  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    If you specify a display, selects it as the current scrolling
    display. This is the default display for the SCROLL, MOVE,
    and EXPAND commands. Although any display may have the scroll
    attribute, note that you can use only the MOVE and EXPAND
    commands (not the SCROLL command) with the PROMPT display.

    If you do not specify a display, the current scrolling display is
    deselected and no display has the scroll attribute.