Designing and Managing Behavior Models - Debugging a Behavior Model - Matching Triggers and Alarm Transitions -
Checking a Poll's Poll Condition      Rules for Matching

Matching Triggers and Alarm Transitions

When a trigger is fired, NerveCenter must decide whether that trigger should cause a state transition in an active alarm instance or cause a new alarm instance to be created. What conditions must a trigger and transition meet before one of these actions takes place?

• A transition whose name matches the name of the trigger must be pending.

  In an active alarm, a transition is pending if its origin state is the alarm instance's current state. A transition is also considered pending if its origin state is Ground. When the second type of transition occurs, a new alarm instance is instantiated.

• The trigger's identity must match the transition's identity.

  Triggers have four-part identities. These identities include a name, a subobject, a node, and sometimes a property. Transitions' identities have the same four parts, plus a fifth part, scope. NerveCenter uses matching rules to compare a trigger's identity to the identity of each pending alarm transition. Each pair of names, subobjects, nodes, and properties must pass a comparison test before a transition takes place.

This section describes the identities of triggers and transitions, specifies the matching rules, and provides examples of objects that match and objects that don't match. See the subsections listed below:

• Identities of Triggers and Transitions
• Rules for Matching
• Examples of Matching Triggers and Transitions

Identities of Triggers and Transitions

The components of a trigger's identity may be supplied by you, the designer, or by NerveCenter, depending on how the trigger is generated. On the other hand, a transition's identity is inherited from an active alarm instance or, if the transition's origin state is Ground, from an alarm definition. The remainder of this section discusses how the components of a trigger or transition's identity are given values.

• Name -- Any string.
  • Trigger -- You give a trigger its name when you define the poll or mask that will fire the trigger, when you make a call to the FireTrigger() function, or when you use the Fire Trigger alarm action. NerveCenter assigns reserved names to built-in triggers.
  • Transition -- You establish a transition's name when you define the transition, in the course of drawing an alarm's state diagram.

• Subobject -- Usually the MIB base object and instance (connected with a period) associated with the condition that prompted the trigger.
  • Trigger -- The subobject of a trigger fired by a poll is taken from the OID used in the SNMP GetRequest that caused the trigger to be fired. Similarly, the subobject of a trigger fired by a trap mask is taken from the OID in the first variable binding in the trap that caused the trigger to be fired. Built-in triggers are assigned a subobject of $ANY.

    For triggers fired as a result of a call to the Fire Trigger () function or by a Fire Trigger alarm action, you specify the subobject when you call the function or define the alarm action.

  • Transition -- In a subobject-scope alarm instance, a transition inherits its subobject from the alarm instance. For example, if an alarm instance tracks ifEntry.2 on a given node, all its transitions do also. If the transition would be an alarm instance's first, it has no subobject. Transitions in node- and enterprise-scope alarms do not have subobjects either.
• Node -- The name of a managed node.
  • The node attribute of a trigger fired by a poll or a mask is assigned the name of the node on which the condition of interest was detected. For triggers fired as a result of a call to the Fire Trigger () function or by a Fire Trigger alarm action, you specify the node when you call the function or define the alarm action.
  • A transition inherits its node from its alarm instance. For example, if an alarm instance tracks node router1, all of its transitions do also. If the transition would be an alarm instance's first, the transition does not have a node. In addition, transitions in enterprise scope alarms do not have nodes.
• Property -- The name of a property or empty.
  • Trigger -- You specify the property of a trigger fired by a Fire Trigger alarm action when you define the action. Triggers from other sources do not have properties.
  • Transition -- A transition inherits its property from the associated alarm definition.
• Scope -- Subobject, Node, Instance, or Enterprise
  • Trigger -- A trigger does not have a scope.
  • Transition -- A transition inherits its scope from the associated alarm definition.