Library /sys$common/syshlp/tcpip$ucp_help.hlb PING, Qualifiers, /PATTERN  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /PATTERN="hexadecimal-string"

    Optional.

    Fills out the packet you send with up to 16 bytes, which is
    useful for diagnosing data-dependent problems. The string is a
    hexadecimal string of up to 32 characters (16 bytes).

    For example, /PATTERN="ff" causes the sent packet to be filled
    with ones (1).