Library /sys$common/syshlp/nclhelp.hlb set, x25_protocol, dte, segment_size  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Default: 64

    Segment unit size specified for data sent at this DTE to be
    used for charging.

    Example:

    set x25 protocol dte dte-1 segment size 64