Library /sys$common/syshlp/uafhelp.hlb MODIFY, Qualifiers, /DIOLM  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /DIOLM=value

    Specifies the direct I/O count limit for the DIOLM field of the
    UAF record. The direct I/O count limit is the maximum number
    of direct I/O operations (usually disk) that can be outstanding
    at one time. The default is 40 on VAX systems and 150 on Alpha
    systems.