Locks a page or range of pages in memory. The specified virtual
    pages are forced into the working set and then locked in memory.
    A locked page is not swapped out of memory if the working set of
    the process is swapped out. These pages are not candidates for
    page replacement and in this sense are locked in the working set
    as well.

    Format

      SYS$LCKPAG  inadr ,[retadr] ,[acmode]

    C Prototype

      int sys$lckpag  (struct _va_range *inadr, struct _va_range

                      *retadr, unsigned int acmode);

1  –  Arguments

 inadr

    OpenVMS usage:address_range
    type:         longword (unsigned)
    access:       read only
    mechanism:    by reference
    Starting and ending virtual addresses of the range of pages to be
    locked. The inadr argument is the address of a 2-longword array
    containing, in order, the starting and ending process virtual
    addresses. Only the virtual page number portion of each virtual
    address is used; the low-order byte-within-page bits are ignored.

 retadr

    OpenVMS usage:address_range
    type:         longword (unsigned)
    access:       write only
    mechanism:    by reference
    Starting and ending process virtual addresses of the pages that
    $LCKPAG actually locked. The retadr argument is the address of
    a 2-longword array containing, in order, the starting and ending
    process virtual addresses.

 acmode

    OpenVMS usage:access_mode
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value
    Access mode to be associated with the pages to be locked. The
    acmode argument is a longword containing the access mode. The
    $PSLDEF macro defines the four access modes.

    The most privileged access mode used is the access mode of the
    caller. For the $LCKPAG service to complete successfully, the
    resultant access mode must be equal to or more privileged than
    the access mode already associated with the pages to be locked.