This screen provides statistics on asynchronous data page
    prefetching.

    Asynchronous prefetching includes both traditional asynchronous
    prefetching ( "APF") when pages are "known" to be needed
    (as during a sequential scan of a storage area) and detected
    asynchronous prefetching ( "DAPF") when a pattern of sequential
    page access is noticed and pages are automatically prefetched in
    anticipation.