Library /sys$common/syshlp/nclhelp.hlb set, hdlc, link, minimum_data_size  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Default: 576           Value: 262-65532

    Minimum number of bytes that users of the data link can specify.
    This number applies to both transmit and receive frames.

    The value of this characteristic must be less than or equal to
    the value of the maximum data size characteristic. You can modify
    this characteristic only when the entity is disabled.