Why doesn't changing a state threshold immediately trigger alarm notifications?

First, some background on state thresholds.

Every state that you add to a parameter is defined by a threshold value. If incoming values cross the threshold in the "away-from-normal" direction, then a state change occurs, and the parameter is regarded as being in the state defined by the threshold. Let's look at a basic example of this:

A state named HIGH has been defined, with a threshold value of 10. This state is located above the NORMAL state, which means when the parameter value increases to 10 or more (i.e. moving in the away-from-normal direction), a state change will occur from NORMAL to HIGH. Since the Raise alarm option is ticked, this state change will trigger an alarm to be raised, and since the Notifications option is set to Active, anyone subscribed to this parameter will receive maintenance-level notifications.

With this in mind: what happens if the current value of param1 is 8, and we edit the state threshold to be 5 instead of 10? Just before trying this, let's check in on the current state of the parameter:

This confirms that param1 is in the NORMAL state, which is to be expected since the current value is 8, which is below the HIGH state threshold of 10.

Now we will edit the HIGH state threshold to be 5:

And immediately check back in on the current state of the parameter:

As expected, the parameter is now in the HIGH state, because the threshold was changed to below the current value of the parameter. However, what's significant is what didn't happen; as hinted at by the question in the title, changing the state threshold didn't trigger any alarm notifications. This is despite the state configuration having Notifications set to Active.

So, why doesn't changing a state threshold immediately trigger alarm notifications?

State change notifications are deliberately suppressed if the reason for the state change is because of an edit made to the threshold value. The reason for this suppression is that state alarms are intended to notify of incoming data crossing a threshold. By changing the threshold, no incoming data has been received; the parameter value is exactly the same before and after the threshold change.

Armed with this piece of knowledge, you can confidently make changes to state thresholds without being concerned that users will receive unwanted notifications based on your configuration changes. Of course, next time new data arrives into the system which causes a state threshold to be crossed, alarm notifications will be sent exactly as configured, based on user subscriptions and notification preferences. You can also read more about how to troubleshoot these alarms and notifications.