Buffered data behavior

The buffered data feature enables efficient accumulation and propagation of VTQ (Value, Time, and Quality) data updates, without folding and data loss, to data consumers such as objects, alarms, the Historian, and scripts from field devices that support buffering.

Buffered data is defined as data captured and stored locally on a remote device for later transfer to a supervisory system for processing, analysis, and long-term storage. The Buffer property is input-only.

When an object is associated with an attribute that supports buffered data (HasBuffer property is true), the object monitors and processes the Buffer property of the attribute. Each VTQ entry in the buffer that meets value deadband criteria is pushed to the Historian.

Attributes that are buffer-enabled are registered to Historian in the same manner as non-buffered attributes are registered. The Historian does not differentiate a buffered from a non-buffered registered attribute. An attribute is considered registered after a Historian key is returned from HCAL to the object.

All the buffered VTQs that are received by the parent attribute while Historian registration is pending are ignored and discarded.

For more information about buffered data, see Enable buffered data. For further reading on historizing events and attributes that are buffering-enabled, see About buffered data and history.