After the PXE asserts a state for a sensor, it may de‑assert the same state later on.
To de‑assert a state is to announce the end of the previously asserted, bad state. Below are good state changes that cause the PXE to de‑assert.
1. above upper critical --> above upper warning 2. above upper warning --> normal 3. below lower warning --> normal 4. below lower critical --> below lower warning |
In the threshold settings dialog, the Deassertion Hysteresis field determines a new level to turn on the "de‑assert" action.
This function is similar to a thermostat, which instructs the air conditioner to turn on the cooling system when the temperature exceeds a pre-determined level. "Deassertion Hysteresis" instructs the PXE to de‑assert a state for a sensor only when that sensor's reading hits the "deassertion" level.
For upper thresholds, this "deassertion" level is a decrease against each threshold. For lower thresholds, this level is an increase to each threshold.
For example:
If Deassertion Hysterresis = 2,
To use each threshold as the "deassertion" level instead of determining a new level, set the Deassertion Hysteresis to 0 (zero).
If you have created an event rule that instructs the PXE to send notifications for deassertion events, setting the "Deassertion Hysteresis" is helpful for eliminating a number of notifications that you may receive in case a sensor's reading fluctuates around a certain threshold.