Redundancy during Run Time

When you deploy these objects to a run-time environment, the configuration objects become the Active object and the Standby object.

• Active object: The object that is currently executing functions. For AppEngines, it is the object that is hosting and executing ApplicationObjects. For data acquisition, it is the object that is providing field device data through the RedundantDIObject.

• Standby object: The object that is waiting for a failure in the Active object or for a force-failover. For AppEngines, it is the object that monitors the status of the Active AppEngine. For data acquisition, it is the object that is not providing field device data through the RedundantDIObject.

In the AppEngine redundancy environment, the Active and Standby objects monitor each other’s statuses and switch during a failover situation.

During a failover, when an Active engine fails, it restarts and the Standby engine becomes active. The Active engine then turns to the standby mode. In the data acquisition environment, the RedundantDIObject monitors the status of the two DIObject data sources, and handles the switching from Active to Standby objects.

The relationship between the configuration time (Primary/Backup) and run-time (Active/Standby) object pairs is not static. In the run time, either the Primary or Backup object can be the Active object at any particular time. Whenever one becomes the Active object, the other automatically becomes the Standby.

Note: In a Redundant Telemetry Server deployment using PCS connectivity to Application Server, failover from the primary Telemetry Server to secondary Telemetry Server is not instantaneous and may take several seconds to complete. During this time, loss of data may occur.