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

    Default: 10            Values: 1-4294967296

    Specifies the minimum time (in seconds) allowed between updates
    of address information. More frequent modification to the set of
    local towers is prohibited.

    Example:

    set session control address update interval 10