State propagation policies

State propagation policies for a dynamic service context determine how the Availability and Performance state of an entity's node and the nodes it impacts change because of events being received to that entity.

When new events occur against a service model member (device, component, component group, logical node, organizing group, or dynamic service) Service Impact identifies all of the service contexts in which that member participates. For each service context, Service Impact performs the following processing:
  • Applies the combination of global, service, and node context policies to decide the state of that member in this service context.
  • If the combination of policies indicate that the event should be propagated further within the service context, looks up all impact dependency relationships that exist for other nodes in the same service context. Different relationships can exist in other service contexts.
  • Applies the service context polices to each of those nodes to compute their new state in the service context and decide whether to continue propagating further. Propagation of state change and event continues until all state and event propagations are completed.
  • If any path through the impact graph affects the dynamic service itself, generates a service event. The service event includes details about the path from the event to the service model member through the impact graph to reach the dynamic service. Multiple paths through the graph from a single member’s event might reach the dynamic service node, and multiple concurrent events to different members. Therefore, details of a service event include the union list of all service event paths and a probability ranking of which path and originating member event is the root cause.

For a service model member that you use only to group child members, you can suppress sending service events.

You can create and assign multiple policies to any service member. In the Impact View, to select the type of policy that you want to create, edit, or view, select the Availability aspect or the Performance aspect.

The policy type that is applied to the members determines which members receive the data. The policy types, in order of precedence are as follows. For more information about state symbols and borders that are shown in the examples, see Actual and derived state.

  1. A contextual policy propagates the member's state change only to its immediate parent members within the current service context.

    In the following example graph, a contextual policy is applied to the service model for Dynamic Service B (DynSvc-B). The policy states that if one child member is down, then the state of DynSvc-B must be degraded.

  2. A global policy applies to all service model contexts that share an member that has a changed state. For example, if a global policy is applied to a member in a service model, and a child member has a change to its state data, the new state is propagated to the parent members in all service models to which the member belongs.

    The following example graph shows that DynSvc-D is used in two different service models: DynSvc-C and DynSvc-E. The global policy propagates the degraded state to all service contexts of which DynSvc-D is a member.

  3. A member with the default policy sends the state data of the worst condition affecting it to its parent member. The default policy is negated if you add either a contextual or global policy to a service model.

    In the following example graph, no policy is applied to DynSvc-B. Its state is down because that is the worst case of its children.

If multiple policies are applied to a member, then the following overrides occur:
  • A contextual policy overrides a global policy.
  • Contextual and global polices override the default policy.