Note that Tuning Policies for a NiagaraNetwork have only 3 properties, as follows:
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Stale Time
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If set to a non-zero value, a subscribed Niagara proxy point becomes “stale” (status stale) if the configured Max Update Time expires without an update from the server (source station). This stale timer is reset upon each subscription update.
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If set to zero (default), the stale timer is disabled, and a subscribed point becomes stale only while the source (server) point is also stale.
Whenever a source point of a Niagara proxy point has a stale status, for example a Bacnet proxy point, the Niagara proxy point
for it will also have a stale status, regardless of this setting.
Stale time is “client side,” whereas the other two “update time” properties affect “server side” operation of the subscription. For example, when a client (Supervisor) station creates subscriptions to a server station (JACE with a field bus), say to update Niagara proxy point values on a Px page, subscriptions are set up with the server to observe rules in the Min and Max Update Time values.
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Min Update Time
The minimum amount of time between updates sent from the server to the client. It is used to throttle data changing at a rate faster than minUpdateTime. Default value is 1 second.
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Max Update Time
Used by the server to resend the values to the client for subscribed points, if values have not been sent for other reasons (such as a change of value or status). Default value is 15 minutes.
Relative to tuning policies in other networks, the importance of NiagaraNetwork tuning policies are typically secondary, and
then only applicable for a station that has proxy points under its NiagaraNetwork. In typical applications, this means the
Supervisor station only.As a general rule, if configuring the Stale Time in a Niagara Tuning Policy, it is recommended to
be greater than the Max Update Time by a factor of three.