Why set ExcMax for an advise point?

The OPC server sends data to advise points whenever a new value is available for the following reasons.

1. The point typically updates slowly, but end users would like to see it update more frequently so that it can be included more easily in displays, rollup calculations, or other analyses.

2. The user wants to record a step trend in the archived data itself instead of setting the step parameter on the point. This way steps are visible even when the data is plotted in a program that is not part of the PI System.

In case (2), AVEVA strongly recommends setting the /TA interface parameter to accomplish the same result without resorting to setting ExcMax on all advise points. For details, please see Why not just use the /TA parameter? below.