Summary Mode for raw historic traces is designed to help your system avoid the performance issues that can occur when traces have high numbers of values. It works by allowing you to define a Point Limit, which sets the maximum number of values that can be represented by a trace (for a Trend’s time range). If the Point Limit is exceeded, ClearSCADA automatically adjusts the trace so that it uses processed historic data instead of raw historic data. This results in a trace that shows a reasonable amount of values and is responsive (a high number of values on a trace can cause slow performance).
For example, if you set the Point Limit to 2000, it means the trace can show up to 2000 values on a single interval (that is, the trace can represent up to 2000 values shown on screen at any one time). If the trace has 2300 values to show, ClearSCADA automatically sets the trace to use processed historic data with an interval of Per Pixel. As a result, the Trend covers the same time range but shows fewer values on the trace. As the values on the trace are now processed, they are not the actual reported values; they are calculated values.
When ClearSCADA has to display a Trend in Summary Mode, it sets the trace to:
- use processed historic data instead of raw historic data
- use an Interval type of Per Pixel.
- use an Algorithm of Max for Bar traces or Min and Max for Step and Line traces. When Min and Max are used, the trace plots the minimum and maximum processed values for each resample interval.
The processed historic data is used as the source data when the trace’s values exceed the Point Limit. If you reduce the interval so that the values are lower than the Point Limit, the trace will revert to using raw historic values again.
Further Information
Processed Historic Data on Trends
Point Limit Setting: see Configure a Trace