6-25 MINI-LINK BAS
EN/LZB 111 0542 P2B Technical Description
6.8 Alarm and Event Management
The alarm and event handling is performed by the HHs.
This means that alarm and event filtering is done as close to the alarm
originating point as possible, so as to avoid overloading of the system
with internal traffic. This also contributes to reduce the complexity of
the management structure because some alarm suppression activities
are already performed at a lower level.
6.8.1 Alarm Correlation
The alarm or event notification is managed by the corresponding HH
instance, the one managing the logical unit that originated the
alarm/event, which filters it according to predefined criteria and by
taking into consideration the actual alarm situation of the unit itself.
This activity, that does not involve other HHs than the one originating
the alarm, is called local alarm correlation.
When it comes to the correlation among alarms coming from different
HHs, it is the alarm handler that takes decisions, by using an alarm
correlation file.
6.8.2 Alarm Suppression
During system restarts the alarms and events are not forwarded to the
management system until the restart has been properly carried out, to
avoid spending time on sending and handling alarms and events that
are of no use to the operator. After the restart is finished, the alarm
notification function is enabled.
It is also possible for the operator to mark an alarm as no-trap, that
means that even if the alarm occurs, no notification will be sent to the
management system.
6.8.3 Active Alarm List
The alarm handler is responsible for keeping a list of active alarms.
This list is updated by the other applications; alarms are also cleared
by the sender. In other words, the alarm handler maintains the list, but
it does not perform any polling activity: it is the responsibility of the
other applications to ask the alarm handler to add a new record to the
list or to remove an existing one, called alarm clearance.
At the restart, the active alarm list is cleared. Thus, the active alarm
list contains only outstanding alarms.
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