History

The Historian receives data only from the active engine. The active engine processes historical data and sends it to the Historian when the Historian is available. If the Historian becomes unavailable, the active engine stores the data locally (in Store Forward History Blocks) and forwards it when the Historian becomes available.

In the meantime, local Store Forward data is transferred to the standby engine via the RMC. When an engine enters Store Forward mode, it synchronizes its data with its partner engine. Store Forward data is transferred (and synchronized) every 30 seconds, so no more than 30 seconds can be lost in the event of an engine failure.

Note: Attributes and tags which were not configured in the Historian before failover are not stored.

History: Redundancy Diagnostics

In order to facilitate management of Store Forward data collected across multiple failures and to improve diagnostics, the active engine has attributes which show the status of Store Forward.

The following information is available:

• Store Forward data has been collected for engine: Engine.Historian.InStoreForward_Standby

• Store Forward data lost: Engine.Historian.StoreForwardDataLost_Standby

• Store Forward data cannot be stored on active engine in store forward mode: Engine.Historian.StoreForwardProblem_Standby