VMS Help Sys Parameters, NET_CALLOUTS  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    NET_CALLOUTS is normally set to 0. A value of 255 indicates that
    no attempt is to be made to assign a new proxy connection to an
    active server, but that a new process must be started to invoke
    the installation security policy callout modules in LOGINOUT.EXE.
    Values 1 through 254 are reserved for future use.

    NET_CALLOUTS is a DYNAMIC parameter.