Logging modes

The Logging mode setting decides what a component sends or writes for the members of its selected tag collections on each interval. There are three modes: Snapshot, On Change and Everything.

The three modes

• Snapshot sends or writes the current value of every collection member on each interval, whether or not the value changed.
• On Change sends or writes only values that have changed.
• Everything sends or writes every sample that arrives, including unchanged values.

Snapshot is the default on every component page that states a default. Everything gives the most detailed recording and the largest volume of data, so choose the mode by the resolution of measurement required.

How the update interval applies

In Snapshot mode the interval is how often the current value of each member is sent or written. In On Change and Everything modes the interval is how often the pending changes or samples are sent, or flushed to the file or database. The MQTT Publisher, the Webhook Publisher, File and tag loggers, and the TAG SQL Historian state this explicitly. The InfluxDB and Prometheus logging and InfluxDB historians pages say that the mode sets what is sent on each interval, and How to log data to the cloud (InfluxDB) describes On Change as sending the changes recorded during the interval.

Components that offer logging modes

These component pages list a Logging mode setting:

• The InfluxDB v1 Logger, on InfluxDB and Prometheus logging.
• The InfluxDB v2 Historian and the InfluxDB v3 Historian, on InfluxDB historians.
• The TAG File Logger and the TAG SFTP Logger, on File and tag loggers.
• The TAG SQL Historian, on TAG SQL Historian.
• The MQTT Publisher, on MQTT Publisher.
• The Webhook Publisher, on Webhook Publisher.
• The Prohelion Cloud Dashboard component, on Prohelion Cloud Dashboard.

The Tag Relay Sender lists a Snapshot interval (seconds) setting and no Logging mode. It sends a full snapshot of the selected collections at a fixed interval, as described on Tag Relay Sender. The How to configure data logging guide shows where to set the mode in the loggers and publishers it covers.