Handling of Tier-2 store-forward events

The QualityDetail information, used to determine if a Wonderware tag is in store-forward on a Tier-1 Historian, is not carried over in the replication process. Therefore, you must use another mechanism for a Tier-2 Historian to determine if a disconnection (that is, a store-forward event) occurs with the source Tier-1 Historians. In order for the connector to detect a Tier-2 store-forward event, you must replicate the SysTimeSec tag from each source Tier-1 Historian to the Tier-2 Historian.

Since this tag updates every second, the connector monitors the replicated values of the tag to check for gaps. If a data gap is detected, all of the tags associated with the source Tier-1 Historian are considered by the connector to be in store-forward and data collection for those tags will be halted. When the gap is no longer present, the connector will attempt to recover history for those tags starting from the original start time of the gap and then continue on to collect the real-time values.