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Events 318
Snapshots and Events
Events can include snapshot functions among their triggers and actions.
Snapshots as Triggers
Events can be triggered by the following snapshot functions:
• Recall of specific snapshots
• Enabling of Snapshot modes (Preview, Update and Edit)
Snapshots as Actions
Event actions can include the following snapshot functions:
• Recall of a specific snapshot
• Recall the previous, next or selected snapshot.
• Initiate Store to Selected Snapshot commands (overwriting and updating snapshots)
• Enable different Snapshot modes (Preview, Update and Edit)
Snapshot Modes and Event Status
While in Update or Edit modes, events-driven snapshot recall is suspended.
While in Preview mode, triggers that occur in the online state of the system are executed, including MTC-driven recall of snap-
shots. Triggers caused by changes to the offline (Preview) controls are ignored and do not cause events to occur.
Avoid Feedback Loops
Because events can both affect and be affected by snapshots, it is possible for events to cause “feedback loops.”
Be especially careful when Recall Previous or Next snapshot triggers and actions are combined with events that recall a specific
snapshot, as shown in the following diagram.
Diagram illustrating potential logic feedback loop between events and snapshots
The global event Disable All and Reset All buttons can serve as “panic” buttons to temporarily suspend and/or reset all events,
giving you a chance to diagnose the source of any problems. For more information, see
Resetting Events.
Event 011
Event 414
Trigger:
Action
Recall of Snapshot 003
:
Recall Next Snapshot
Recall of Snapshot 004
Trigger:
Action:
Recall Previous Snapshot
Result: Snapshot 004
Result: Snapshot 003 is recalled
Snapshot 003 is recalled (manually, MTC, other)
is recalled
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