Summary actions

A summary action is a set of aggregation calculations to be performed on a set of tags between a start time and an end time with a defined resolution. When you configure a summary action, you must define the type of aggregation you want to perform (called a summary operation) and the analog tags that you want to be summarized. The Classic Event subsystem performs average, minimum, maximum and sum calculations on the basis of a specific event being detected.

Note: Summary actions using the Classic Event subsystem are retained for backward compatibility. We recommend that you use the more robust and flexible Replication subsystem to perform data summaries. For more information, see Manage and configure replication.

Data summaries are useful for:

• Extremely long-term data storage. Because summarized data takes up less space than full resolution data, even a moderately sized system can store daily summary information for many years.

• Production reporting. For many reporting purposes, aggregate data is more important than raw data. For example, the total mass produced in a day is often more relevant than the actual rate of production during the day.

• Integration with business systems. The full resolution, high-performance AVEVA Historian history and real-time data tables are best accessed with tools that can take advantage of the AVEVA Historian time domain extensions. However, not all client tools support these SQL extensions. The summary tables reduce the volumes of data to manageable quantities that can be used by any normal SQL client application.

A summary action is usually triggered by a schedule detector. However, you can perform a summary as a result of any event detection.

Tag values with bad quality are not filtered out before the aggregation is performed. To perform an aggregation with only good quality, for example, use a generic SQL action that executes an aggregation calculation query on the History table where the value of the Quality column equals 0.

The results of all summaries are stored in the SummaryData table in the Runtime database.

Important: Use caution when setting up summary actions. Using a high resolution for your summary queries can have a negative impact on the overall performance of the system.

Average, minimum, and maximum values can also be determined by using the time-weighted average, minimum, and maximum retrieval modes, respectively. For more information on these retrieval modes, see Explore retrieval modes in the AVEVA Historian Retrieval Guide. Keep the following in mind when deciding to use either the event summaries or the retrieval modes:

• For the time-weighted average retrieval mode, the amount of time between the data values is a factor in the average, whereas the event summary action is a straight statistical average. For more information, see Average retrieval.

• Performing an average at retrieval eliminates problems that occur during Daylight Savings Time adjustments for schedule-based summaries. For more information, see Schedule detectors.

For a comparison of all the different types of summaries that the AVEVA Historian supports, see Querying aggregate data in different ways in the AVEVA Historian Retrieval Guide.