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In order to cover data loss during a keep alive timeout scenario, the MQTT Transmission History Store includes a Rolling History Buffer that can be configured in the Advanced Properties configuration section. When the Rolling History Buffer is enabled, all tag changes will be written to the History Store regardless of connection status.

The Metrics Stored tag for the History Store will update as data is written to and pruned from the Rolling History Buffer. 

• Enable Rolling History Buffer
  • Enable the Rolling History Buffer to store data in a rolling buffer to cover data loss in a keep alive timeout scenario
• Rolling History Prune Interval
  • Interval at which to attempt to prune the rolling history buffer in seconds
• Rolling History Max Age
  • The maximum age allowed of the data in the rolling history buffer in seconds
  • All data older than the Max Age will be pruned at each prune interval
• Rolling History Prune Quantity (Deprecated in release 4.0.19)

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