/SYSTEM
       /NOSYSTEM

    Controls whether the DELETE command deletes files with the file
    type SYS. Files with the type SYS are usually necessary for the
    operation of an RT-11 system. Only RT-11 volumes handle .SYS
    files in this manner.

    The default is /NOSYSTEM; the DELETE command does not delete
    an RT-11 file with the SYS type, whether matched by a wildcard
    specification or explicitly named. EXCHANGE displays a message
    whenever it skips a SYS file during a delete operation.