Process late data at run time

Data received by Application Server run-time clients from the Telemetry Server or other sources may arrive late, especially when using publish/subscribe models such as MQTT, with or without Sparkplug B. "Late data" refers to process data that is received after the time of the actual event. For example, an OMI ViewApp may receive data along with its VTQ timestamp x number of minutes or even hours after the triggering event has occurred.

Application Server allows late data received through a DI Object to backfill historical data in the Historian while presenting live data to run-time visualization clients, such as OMI ViewApps. Note that value historization is done only for attributes that have the History extension enabled. Late data received from direct references or through Multi-Galaxy Communication is not sent for historization.

When connection to Application Server from the data source is lost, historical data is backfilled once the connection is restored. References to ScanGroup items directly in scripts allow late data to be processed. For example, "me.Int1 = DiObject.Scangroup.Item1" assigns late data values to user-defined attribute (UDA) Int1.

Late data received from DI objects referenced through the I/O extension is not backfilled. In the meantime, Application Server provides run-time clients (AVEVA OMI and/or InTouch HMI workstations) with last known good value, and resumes the live data feed when the connection is restored. Historical data is sent directly to the Historian and does not affect either Application Server or the run-time clients.

While the Historian is processing the historical data, Application Server uses a Quality and Status animation, "Processing Historical Data," to notify the run-time clients that this is occurring, while continuing the live data feed to the run-time clients. At the end of the historical data processing, the current data/states/values are determined based on either the live data or, in the absence live data, by using the last-known good values from the historical data. Trend pens, the Trend Client, and any other visualized data that relies on historical data are updated when historization is finished.

The historical data is historized appropriately and can be later queried as if it had been received in order.