Tuning properties provide rules for evaluating when JSON outputs data and for indicating an update strategy. Configuring this policy can affect system performance. They are located in the Schema Config folder.

Figure 8.   Tuning policy properties

Update Strategy determines when JSON string generation occurs: at change-of-value or on demand.

There is a built-in Min Write Time to ensure that hundreds of concurrent CoV changes over a short time do not result in a deluge of JSON messages. For example, when set to five (5) seconds and a change-of-value occurs within five seconds of the last change of value, schema generation defers for a full five seconds. However, if this amount of time exceeds the Max Write Time setting, the system forces schema generation. In contrast, Max Write forces an update after the specified interval.

Export markers applied to numeric points also have a CoV Tolerance property which can be used to throttle output.

The Write On Start and Write On Enabled properties provide other ways to invoke schema generation, for example, when the station starts.