Glossary · HMI, SCADA and operations
Historian
Also known as: Process historian, Plant historian, Data historian
German: Prozessdatenarchiv
In industrial automation, a historian is a time-series database system that collects, compresses, stores and serves process data, events and alarms from control systems over long periods for trending, reporting and analysis.
- HMI and SCADA
- Process industry
In one sentence
A historian is a time-series database that collects and stores process data and events from control systems for trends, reports and analysis.
Example
The plant historian stores 50,000 tags at one-second resolution for five years, and process engineers use it to compare today's batch with the best batch of last year.
How it applies
- Engineering: Historians collect data via OPC, native drivers or MQTT, often through collectors that buffer during network outages (Store-and-forward). Compression settings determine what detail is retained; configure them per tag.
- Operation: Historians feed trends, reports, dashboards and analytics, including training data for machine learning. Time synchronization across sources is essential for correct sequence of events.
- Compliance and security: In regulated plants, historian data can be GMP records. Historians often sit in a DMZ between OT and IT networks.
- Documentation: Document tag naming, units, compression, retention and data sources. Data users need to know whether a value is raw, compressed or interpolated.
Historian vs. archive tag
An Archive tag is a recorded variable inside one HMI or SCADA project. A historian is a separate, scalable system that aggregates data from many systems over long periods.