VMS Help EXCHANGE, DIRECTORY, Qualifiers, /BADBLOCKS  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /BADBLOCKS
       /NOBADBLOCKS

    Scans the volume to find any blocks that return read errors. The
    data on the volume is not modified. If a bad block replacement
    table is present, the contents of the table are displayed. This
    is valid for RT-11 volumes only.