start_va_64

    OpenVMS usage:address
    type:         quadword address
    access:       read only
    mechanism:    by value
    The starting virtual address of the pages to be unlocked. The
    specified virtual address will be rounded down to a CPU-specific
    page boundary.

 length_64

    OpenVMS usage:byte count
    type:         quadword (unsigned)
    access:       read only
    mechanism:    by value
    Length of the virtual address space to be unlocked. The specified
    length will be rounded up to a CPU-specific page boundary so that
    it includes all CPU-specific pages in the requested range.

 acmode

    OpenVMS usage:access_mode
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value
    Access mode on behalf of which the request is being made. The
    acmode argument is a longword containing the access mode.

    The $PSLDEF macro in STARLET.MLB and the file PSLDEF.H in
    SYS$STARLET_C.TLB define the following symbols and their values
    for the four access modes:

    Value      Symbolic Name      Access Mode

    0          PSL$C_KERNEL       Kernel
    1          PSL$C_EXEC         Executive
    2          PSL$C_SUPER        Supervisor
    3          PSL$C_USER         User

    The most privileged access mode used is the access mode of the
    caller. To unlock any specified page, the resultant access mode
    must be equal to or more privileged than the access mode of the
    owner of that page.

 return_va_64

    OpenVMS usage:address
    type:         quadword address
    access:       write only
    mechanism:    by 32- or 64-bit reference
    The lowest process virtual address of the unlocked virtual
    address range. The return_va_64 argument is the 32- or 64-bit
    virtual address of a naturally aligned quadword into which the
    service returns the virtual address.

 return_length_64

    OpenVMS usage:byte count
    type:         quadword (unsigned)
    access:       write only
    mechanism:    by 32- or 64-bit reference
    The length of the virtual address range unlocked. The
    return_length_64 argument is the 32- or 64-bit virtual address
    of a naturally aligned quadword into which the service returns
    the length of the virtual address range in bytes.