VMS Help LANCP, DEFINE, NODE, Qualifiers, /SIZE  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /SIZE=value
       /NOSIZE

    Specifies the size in bytes of the file data portion of each
    downline load message. The default is the load data size
    specified for the device. The permitted range is 246 to 1482
    bytes. Use a larger size for better load performance and less
    server overhead.

    If you do not specify the /SIZE qualifier, the setting remains
    unchanged. The /NOSIZE qualifier clears the setting.