Full retrieval

In full retrieval mode, all stored data points are returned, regardless of whether a value or quality has changed since the last value. This mode allows the same value and quality pair (or NULL value) to be returned consecutively with their actual timestamps. It works with all types of tags.

By using full retrieval in conjunction with storage without filtering (that is, no delta or cyclic storage mode is applied at the Historian), you can retrieve all values that originated from the plant floor data source or from another application.

Full retrieval best represents the process measurements recorded by the Historian. However, it creates a higher load for the server, the network and the client system because a very large number of records may be returned for longer time periods.

For full retrieval for replicated summary tags on a tier-2 historian, if a point with doubtful quality is returned as the result of a value selection from an input summary point with a contained gap, the same point can be returned again with good quality if the same value is selected again from the next input summary point that has good quality.