Alarm triggering logic

Each alarm class is organized into a hierarchy of five severity levels from Normal to Critical. An alarm is triggered when a threshold value is reached that evaluates to true against a combination of alarm class and alarm severity level. Note that a severity level of Normal does not trigger an alarm.

The alarm severity and corresponding threshold value can be set for every numerical attribute. The NMS service on each Admin Node continuously monitors current attribute values against configured thresholds. When an alarm is triggered, a notification is sent to all designated personnel.

Attribute values are evaluated against the list of enabled alarms defined for that attribute in the Alarms table on the Alarms page for a specific service or component (for example, LDR > Storage > Alarms > Main). The list of alarms is checked in the following order to find the first alarm class with a defined and enabled alarm for the attribute:
  1. Custom alarms with alarm severities from Critical down to Notice.
  2. Global Custom alarms with alarm severities from Critical down to Notice.
  3. Default alarms with alarm severities from Critical down to Notice.

After an enabled alarm for an attribute is found in the higher alarm class, the NMS service only evaluates within that class. The NMS service will not evaluate against the other lower priority classes. That is, if there is an enabled Custom alarm for an attribute, the NMS service only evaluates the attribute value against Custom alarms. Global Custom alarms and Default alarms are not evaluated. Thus, an enabled Global Custom alarm for an attribute can meet the criteria needed to trigger an alarm, but it will not be triggered because a Custom alarm (that does not meet the specified criteria) for the same attribute is enabled. No alarm is triggered and no notification is sent.