Setting this administratively sets the overload bit for the level, and the overload bit continues to be set if the implementation runs out of memory independent of this variable. Setting it true is the deliberate, admin-triggered way to make the router announce itself as overloaded so other routers stop using it as a transit hop while still accepting traffic destined for its own directly attached prefixes -- a common technique for gracefully draining traffic before a planned reboot. For example, an admin about to reload a core router for a software upgrade sets ciiSysLevelSetOverload to true first, waits for transit traffic to drain onto alternate paths, and only then proceeds with the reload.