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Operational historian refers to a database software application that logs or historizes time-based process data. Historian software is used to record trends and historical information about industrial processes for future reference. It captures plant management information about production status, performance monitoring, quality assurance, tracking and genealogy, and product delivery with enhanced data capture, data compression, and data presentation capabilities.
Operational historians are like enterprise historians but differ in that they are used by engineers on the plant floor rather than by business processes. They are typically cheaper, lighter in weight, and easier to use and reconfigure than enterprise historians. Having an operational historian enables "at the source" analysis of the historical data that is not typically possible with enterprise historians.
Typically, these applications offer two layers of data access: through a dedicated SDK(Standard Development Kit)(sometimes in two different flavours: full administration API(Application Programming Interface) and high-speed read/write API), as well as user front-end tools (for instance, administration panels, engineering consoles or portal-like web clients).
Because these applications are designed to fulfil specific operation time requirements, their marketing materials often indicate that these are real-time database systems. However, since such performance measurements are often executed for atomic operations (especially write operations), not necessarily whole transactions, not all of the operational historians must be in fact real-time databases.
Usual challenges the operational historians must address are as follows:
- data collection from real-time external systems,
- storage and archiving of very large volumes of data,
- tag organisation (typically time series, where a single sample contains the information about the time stamp, the value and the sample quality),
- basic data limit monitoring (alarms) and user prompts (messages),
- performance of read and write operations.
As opposed to enterprise historians, the data access layer in the operational historian is designed to offer sophisticated data fetching modes without complex information analysis facilities. The following settings are typically available for data access operations:
- Data scope (single point, history based on time range, history based on sample count),
- Request modes (raw data, last-known value, aggregation, interpolation),
- Sampling (single point, all points without sampling, all points with interval sampling),
- Data omission (based on the sample quality, based on the sample value, based on the count).
Even though the operational historians are rarely relational database management systems, they often offer SQL-based interfaces to query the database. In most of such implementations, the dialect does not follow the SQL standard in order to provide syntax for specifying data access operations parameters.
- Aspen Technology InfoPlus.21 
- Automsoft rapidHistorian 
- Canary Labs Canary Enterprise Historian
- Capstone Technology dataPARC PARCserver
- DOT Systems PulsarTSDB
- GE Intelligent Platforms Proficy Historian
- GP Strategies EtaPRO
- Honeywell Uniformance PHD
- Iconics Hyper Historian
- Inductive Automation SQL Bridge module of Ignition SCADA
- Industrial Cloud Solutions HistorianIQ
- InStep Software eDNA
- Invensys Wonderware Historian
- MatrikonOPC Desktop Historian
- National Instruments Citadel, used in LabVIEW DSC and other products
- Ocean Data Systems Dream Report
- OSIsoft - PI
- Parsec Automation HISTORITrak, a module of TrakSYS
- Polyhedra Historian, a module of Enea's Polyhedra DBMS
- Prediktor Apis OPC Historian
- Rockwell Automation FactoryTalk Historian
- Yokogawa Exaquantum Historian
- Nimbits Cloud Platform for Data Acquisition, Monitoring and Response
- OpenTSDB Scalable Time Series Database
- R. H. (Rick) Meeker, Jr. (13 January 1999). "A Practical Guide to Process Data Historians and Process Information Systems" (PDF). TAPPI. Retrieved 14 September 2012.
- "Globalspec Historian Article". Retrieved 12 Jul 2012.
- Wonderware Historian - Example of naming the operational historian the real-time database
- aspenONE MES Brochure (PDF), Aspen Technology, Inc., 2014, p. 2, retrieved 30 July 2014
- rapidHistorian Brochure (PDF), Automsoft, 2013, retrieved 30 July 2014
- PulsarTSDB Leaflet (PDF), DOT Systems, 2012, retrieved 30 July 2014
- Datasheet: Proficy Historian 5.5 (PDF), GE Intelligent Platforms, Inc., 2013, retrieved 30 July 2014
- Uniformance PHD Product Information Note (PDF), Honeywell International Inc., 2013, retrieved 30 July 2014
- High-Powered Data Acquisition, Inductive Automation, 2014, retrieved 30 July 2014
- eDNA Real-Time Historian, InStep Software, LLC, 2014, retrieved 30 July 2014
- Wonderware Historian Software Datasheet (PDF), Invensys Systems, Inc., 2013, retrieved 30 July 2014
- Logging Data with National Instruments Citadel, National Instruments Corp., 19 July 2012, retrieved 30 July 2014
- Dream Report Brochure (PDF), Ocean Data Systems Ltd., 2012, retrieved 30 July 2014
- TrakSYS Operations Historian (PDF), Parsec Automation Corp., 2012, retrieved 30 July 2014
- Handling time-series data in Polyhedra IMDB, Enea AB, 11 May 2012, retrieved 30 July 2014
- Exaquantum delivers Production Excellence (PDF), Yokogawa Marex Limited, 2013, retrieved 30 July 2014