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

       /SIZE=[size of reserved memory, unit: MB]

    Specifies the number of megabytes to be deducted from the
    system's fluid page count for this memory-resident global section
    when the VMS$RESERVED_MEMORY.DATA data file is read during system
    initialization. The default value for /SIZE is taken from the
    existing Reserved Memory Registry.