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

    Default: 60            Value: 1-16383

    Time (in seconds) to be used for the window timer. When the
    transport service provider has no TPDUs to send over a transport
    connection, it retransmits the last AK TPDU at the specified
    frequency to prevent expiration of the remote NSAP's inactivity
    timer. This attribute is valid for protocol class 4 only.

    set  [node node-id] osi transport template template-id -
         keepalive time integer

    Example:

    set osi transport template osit$loop_clns -
         keepalive time 60