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

    Default: True          Value: True or false

    Specifies whether Session Control should attempt to update the
    ACS (access control set) of the node object whenever it attempts
    to update the towers attribute for the node in the namespace.

    Example:

    set session control modify acs true