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Understanding Transient Resource States

The state of the resource goes from STARTING to UP without SSM having to execute any STARTING_UP action, even if the actions table defines a STARTING_UP action.

transient states

States such as STARTING, which change to something else without SSM intervening.

stable states

States that do not change, unless SSM takes action.

The events that cause a resource to change state usually are external events that rules can interpret, such as system messages or commands the operator issues. However, actions that are defined in the action table of the SSM also can trigger state changes.

A single SSM action can also cause two or three events to occur in sequence. For example, when the TSO resource is DOWN and the desired state is set to UP, SSM executes a START TSO action. This action causes two separate state-changing events to happen for the same resource: