EMS Manual

Generating Standard Events
EMS Manual—426909-005
10-5
Task 2.4: Identify the Events for Your Subsystem
1. Define the valid states of your object.
2. Define the valid transitions between these states.
3. Define the possible conditions (induced internally or externally to your subsystem)
that cause each transition.
4. Define the actions for operators or your subsystem to take after the transition (for
example, report an EMS event, or restart the object).
The semantics of your object states reflect your object, and will vary between objects
and subsystems. For uniformity in object states among subsystems, standard events
define three object states:
The event type of the standard event identifies the reported operational state.
Identify these operational states from your object states.
For an illustration of state transition diagrams and the relationship between operational
states and object states, see Example of a Fictitious NonStop Kernel Subsystem on
page 10-31.
For a description of the conditions you should consider in addition to the normal states
of your object, see Task 3. Generate Standard Events for Your Subsystem on
page 10-6.
Task 2.4: Identify the Events for Your Subsystem
One action in a state transition might be to generate an EMS event message indicating
a change in your object that merits the attention of operators or management
applications.
When to Generate Events

Generate a standard event if the condition that caused the state change is one of
the conditions defined in Section 9, Standard Events.

Define your own events if the condition is not one of the standard conditions
(described later).
When to Not Generate Events
When your object changes state and reports an EMS event message, the operators or
management applications will probably issue commands to direct the recovery of your
object or inquire more about the state of your object.
Object State Standard Event Object Is Reported In
Available Object Available
Unavailable Object Unavailable
Other (persistent, need operator to change) Object Other State Change