About Recovery Mode

Normally, the collector operates in real-time mode. Real-time mode is when the Server-to-Server Collector is polling or is subscribed to events and fires calculations based on these events occurring in real-time. Messages are also sent as they occur. Recovery mode allows you to recover tag and alarm data when the connection between the collector and the source server is re-established. After a connection loss, the configuration settings for the Server-to-Server Collector determine how much tag and alarm data is recovered and if messages are included in the recovery.

The default recovery time is 4 hours. You can disable recovery mode by setting the Max Recovery Time on the Configuration tab of the Collector Maintenance screen to 0 hours.

When Does Recovery Occur?

Recovery mode executes:
  • On Calculation Collector and Server-to-Server Collector start-up.
  • When the collector is resumed after a pause.
  • When there is an on-the-fly change (similar to a pause and resume). Only tags in the new tag con- figuration are recovered.
  • When there has not been a collector stop and start, but the connection to the source archiver is restored.

What Happens When Recovery Occurs?

Upon connecting to the source archiver, in recovery mode, the collector will:
  • Set up subscriptions for all alarms and trigger tags.
  • Perform recovery in time order, oldest to newest.
  • Perform message recovery, if enabled.
  • Begin polling and processing subscriptions in real-time mode.
The items recovered are:
  • Event-based tags

    This includes the data from the last write time until now. The system retrieves all tags.

  • Messages

    The system checks for new messages and verifies errors. Once the system verifies a connection to the destination, it sends the messages one at a time.

  • Alarm Data

    This includes all alarm data from the last write time until now.

Note: Alarm recovery uses a different write time than tag recovery. Alarm recovery starts from the time of the last alarm replicated to the destination.

If your formula contains tags not in the trigger list or dependencies exist among tags (for example, if a calculation tag is a trigger for another calculation tag), then you might not recover all data.