Value capture for event frames and transfers

To display values for an event frame or transfer, PI AF executes data references to retrieve associated attribute values for the time period. You can, however, use Capture Values to save those values in a PI AF database table (AFEventFrameAttributeValue). Doing this can improve performance, since it is faster to display the saved values than to retrieve them.

You can also use Capture Values to ensure attribute values displayed for event frames are the same at any future point as when they were captured. Additionally, Capture Values provides a way to preserve values that might not be available later, such as streaming data that is not persisted long-term.

Value recapture

Automatic recapture occurs whenever the start time and end time of a captured event frame or transfer is modified.

Whenever you add new attributes to an event frame or transfer, you must recapture values to ensure that values are also captured for the new attributes.

Note that when you recapture values, data loss can occur if a data reference has changed since the initial value capture: For example, if values in a table accessed by a table lookup data reference have been modified.