Hold-set timers are used to dampen the effect of a flapping event. A flapping event is where the event continually transitions between clear and set. The hold-set value is loaded into a hold-set timer that prevents a set event from transitioning to the cleared state until it expires.
Each time an event transitions between cleared and set, the timer is loaded and begins to count down to zero. If the timer reaches zero, the event is allowed to enter the cleared state again. Entering the cleared state is always dependent on the object controlling the event conforming to the requirements defined in the event. It is possible, on some event types, to have a further set action reload the hold-set timer. This extends the time that must pass before the hold-set timer expires, and the event enters the cleared state.
For an example of a hold-set timer setting, see LAG degrade priority event.