# Polyhedra (software)

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**Polyhedra** is a family of [relational database management systems](/source/Relational_database_management_system) offered by [ENEA AB](/source/ENEA_AB), a [Swedish](/source/Sweden) company. The original version of Polyhedra (now referred to as Polyhedra IMDB) was an [in-memory database management system](/source/In-memory_database) which could be used in [high availability](/source/High_availability) configurations; in 2006 Polyhedra Flash DBMS was introduced to allow [databases](/source/Database) to be stored in [flash memory](/source/Flash_memory).[2] All versions employ the [client–server model](/source/Client%E2%80%93server_model) to ensure the data are protected from misbehaving application software, and they use the same [SQL](/source/SQL), [ODBC](/source/ODBC) and [type-4 JDBC](/source/JDBC_type_4_driver#Type_4_Driver_-_Native-Protocol_Driver) interfaces. Polyhedra is targeted primarily for [embedded](/source/Embedded_system) use by [original equipment manufacturers (OEMs)](/source/Original_equipment_manufacturer), and big-name customers include [Ericsson](/source/Ericsson), [ABB](/source/ABB_Group), [Emerson](/source/Emerson_Electric_Company), [Lockheed Martin](/source/Lockheed_Martin), [United Utilities](/source/United_Utilities) and [Siemens AG](/source/Siemens_AG).

## Company

Polyhedra development was started in 1991 by Perihelion Technology Ltd, a subsidiary of [Perihelion Software Ltd](/source/Perihelion_Software) (PSL); initially, the project had a working title the "Perihelion Application Toolkit", but was soon renamed Polyhedra (using a left-over trademark from another PSL project). There was a management buyout of PTL in 1994, and the company name changed to Polyhedra plc to match the name of the product. Polyhedra plc was in turn acquired by Enea AB in 2001.[3][4]

## Features

Tim King, the founder of [Perihelion Software Ltd](/source/Perihelion_Software), developed a relational DBMS for historical data as part of his PhD work;[5] Dave Stoneham, who set up PTL, had previously developed a [SCADA](/source/SCADA) system. Building on these experiences, Polyhedra was originally developed "to bring the benefits of relational technology to the embedded market". To this end, it had to be small footprint, very fast... and it had to avoid the need for [polling](/source/Polling_(computer_science)), which is a performance killer. Consequently, it was designed from the start to:

- keep the working copy of the data in-memory (though there is now a variant that keeps the data in a [flash](/source/Flash_memory)-based file);
- use a client–server architecture to protect the data from corruption by rogue application code;
- have an 'active query' mechanism to update client applications when relevant database changes occur;
- have a very simple processing model where a [transaction](/source/Database_transaction) is either a schema change, a query, or a request for a set of inserts, updates and/or deletes - such alterations can either be expressed via SQL statements or by updating through the active queries with (in conjunction with active queries) an [optimistic concurrency mechanism](/source/Optimistic_concurrency_control) to handle clashing updates;
- have a table [inheritance](/source/Inheritance_(object-oriented_programming)) mechanism which, when combined with [Database triggers](/source/Database_trigger) (via the CL language, see below), allows the database designer to program the database in an object-oriented fashion. Table inheritance also avoids or reduces the need for supplementary tables whose primary key is a foreign key to another table, and thus can simplify many queries and updates.
- have a [Historian](/source/Operational_historian)[6] module to allow large volumes of times-series data to be captured, stored, archived and queried in an efficient fashion.

Polyhedra IMDB achieves data persistence through the use of [snapshots](/source/Snapshot_(computer_storage)#In_databases) and [journal logging](/source/Transaction_log); Polyhedra Flash DBMS uses [shadow paging](/source/Shadow_paging), with 2 levels of recursion. In addition, Polyhedra can be used in [hot-standby](/source/Hot_spare) configurations for improved [availability](/source/Availability). The transactional model used by all Polyhedra products ensures atomicity, consistency and isolation (as defined by the [ACID](/source/ACID) properties); durability is enforced in Polyhedra Flash DBMS, while in Polyhedra IMDB clients can choose the durability model when they issue their transactions.

"The Polyhedra DBMS system is fundamentally different compared to other relational systems, because of its active behaviour. This is achieved through two mechanisms, active queries and by the control language (CL). An active query looks quite like a normal query where some data is retrieved and/or written, but instead the query stays in the database until explicitly aborted. When a change in the data occurs that would alter the result of the query, the application is notified. The CL, which is a fully object-oriented script language that supports encapsulation, information hiding and inheritance, can determine the behaviour of data in the database. This means that methods, private or public, can be associated with data performing operations on them without involving the application."[7]

Polyhedra is not a general-purpose DBMS, as the restricted transactional model does not meet all needs, and its fault-tolerance model is based on the hot-standby approach (to minimise hardware costs) rather than [clustering](/source/Computer_cluster) (which is better for load-sharing). However, its limitations are benefits in embedded use, where the emphasis in a deployed application is on performance and cost rather than handling continually varying usage patterns.

Most of the Polyhedra products are made available for purchase under a [proprietary](/source/Proprietary_software) license, but in 2012 Enea released Polyhedra Lite under a freeware license.[1]

## Release history

- 1991 Development started.
- 1993 **Polyhedra 1.0**: first commercial release of an in-memory [Relational DBMS](/source/DBMS#Relational_DBMS) (RDBMS).
- 1995 Ported to [Windows](/source/Microsoft_Windows) and [Linux](/source/Linux).
- 1996 **Polyhedra 2.0**: added [hot standby](/source/Hot_spare) configurations for use in applications needing [high availability](/source/High_availability). First port to an [RTOS](/source/RTOS) ([pSOS](/source/PSOS_(real-time_operating_system)))
- 1997 **Polyhedra 3.0**: new in-memory data storage engine, for improved space and time efficiency.
- 1999 **Polyhedra 3.1**: adds new data types, [ODBC](/source/ODBC) [API](/source/API). [OSE](/source/Operating_System_Embedded) port.
- 2001 **Polyhedra 4.0**: [JDBC](/source/JDBC) support, additional index type, read-only replicas, multi-threading.
- 2002 **Polyhedra 4.1**: [client–server](/source/Client%E2%80%93server) comms overhauled for substantial performance improvements, especially for client apps using the ODBC API (now deemed the 'native' [API](/source/API) for all platforms).
- 2003 **Polyhedra 5.0**: [UNICODE](/source/UNICODE), schema migration ([SQL 'ALTER TABLE'](/source/Alter_(SQL))).
- 2004 **Polyhedra 6.0**: 64-bit support re-introduced, for [Linux](/source/Linux) and [Solaris](/source/Solaris_(operating_system)). (It previously had been available on [DEC Alpha](/source/DEC_Alpha) under [Digital UNIX](/source/Tru64_UNIX) until usage of that platform generally died out.) Polyhedra64 has subsequently been ported to [Windows x64](/source/Microsoft_Windows#64-bit_operating_systems).
- 2006 **Polyhedra Flash DBMS** introduced, based on a fork of the Polyhedra IMDB code base.
- 2007 **Polyhedra 7.0**: Polyhedra IMDB and Polyhedra Flash DBMS code bases unified, for ease of support and greater commonality of features. Also, enhanced resource management and multi-threading.
- 2008 **Polyhedra 8.0**: Polyhedra Flash DBMS now supports [hot standby](/source/Hot_spare) configurations for use in applications needing [high availability](/source/High_availability), in a similar way to Polyhedra IMDB. Polyhedra 8.1 added Linux/MIPS support, the ability to monitor active queries, and enhancements to the historian.
- 2009 **Polyhedra 8.2**: Linux ODBC drivers and IPv6
- 2010

- - - **Polyhedra 8.3**: Some SQL enhancements and streaming output from historian. - **Polyhedra 8.4**: performance enhancements

- 2011 **Polyhedra 8.5**: better integration with 3rd-party tools, and improved performance on Windows. Replica servers can be used in a fan-out configuration for better scaling.
- 2012 **Polyhedra 8.6**: 64-bit integer data type. **Polyhedra Lite** introduced:[1] a free-to-use, reduced-functionality version of Polyhedra32 IMDB, available for Windows, and for Linux on x86 and the [Raspberry Pi](/source/Raspberry_Pi).[8]
- 2013

- - - **Polyhedra 8.7**:[9] [locking](/source/Locking_(computer_science)#Database_locks) and [cascaded deletes](/source/Propagation_constraint). - **Polyhedra 8.8**:[10] [encrypted](/source/Encryption) communications

- 2014 **Polyhedra 8.9**: SQL enhancements ([GROUP BY and HAVING](/source/SQL#Queries), DISTINCT, [outer joins](/source/Join_(SQL))), security enhancements, and online backups for time-series data.
- 2015 **Polyhedra 9.0**: read-only partial database replication via a subscription mechanism, an [ADO.NET data provider](/source/ADO.NET_data_provider) for Polyhedra, and enhancements to the proprietary 'callback API' that can yield significant performance enhancements.
- 2016 **Polyhedra 9.1**: bi-directional subscription and partial table replication, internal resource monitoring, and a [Python](/source/Python_(programming_language)) DB-API module with extensions for Polyhedra-specific features such as active queries.
- 2017

- - - **Polyhedra 9.2**: reduced memory usage, RDI (Remove Device Interface) API, [OPC UA](/source/OPC_Unified_Architecture) RDI, and SQL EXPLAIN command. - **Polyhedra 9.3**: server initiated replication.

- 2018 **Polyhedra 9.4**: Embedded database API and limited SQL function-based indexes.
- 2019 **Polyhedra 9.5**: Backup standby, MQTT interface and Grafana interface.
- 2020 **Polyhedra 9.6**: REST API, WebSocket Server and IMDB API Enhancements.
- 2021 **Polyhedra 9.7**: IMDB API BLOB caching, multiple database support.
- 2022 **Polyhedra 9.8**: Maintenance release, updates for supported OS versions.
- 2023 **Polyhedra 9.9**: Maintenance release, updates for supported OS versions.
- 2024 **Polyhedra 9.10**: Maintenance release, updates for supported OS versions.
- 2025 **Polyhedra 9.11**: Support for User mode Linx interprocess communication, updates for supported OS versions.

## References

1. ["Polyhedra® Lite In-Memory Relational Database System Freeware Available Now from Enea"](http://eecatalog.com/embeddedlinux/2012/10/11/polyhedra-lite-in-memory-relational-database-system-freeware-available-now-from-enea/), Press Release, EECatalog.

1. [Enea Announces Flash-Based Relational Database Management System](http://www.enea.com/templates/Extension____8923.aspx) [Archived](https://web.archive.org/web/20080517120341/http://www.enea.com/templates/Extension____8923.aspx) 17 May 2008 at the Wayback Machine

1. Business Wire: [Enea Acquires Polyhedra](http://www.allbusiness.com/technology/software-services-applications/6050443-1.html)

1. thefreelibrary.com: [Enea Acquires UK Company Polyhedra - Strengthens OSE With Database Technology](http://www.thefreelibrary.com/Enea+Acquires+UK+Company+Polyhedra+-+Strengthens+OSE+With+Database...-a072311343)

1. [Tim King – Home Page](http://www.tim-king.com/)

1. ["Handling time-series data in Polyhedra IMDB"](http://developer.polyhedra.com/polyhedra-features/historian), White Paper, Enea.

1. Aleksandra Tešanović, Dag Nyström, Jörgen Hansson, Christer Norström: [Embedded databases for embedded real-time systems: a component-based approach](http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.23.6688) (2002)

1. ["Free real-time relational database for the Raspi"](http://www.raspberrypi.org/phpBB3/viewtopic.php?t=20065&p=330703), Raspberry Pi forum.

1. ["Embedded DBMS gains locking and cascaded deletes"](http://linuxgizmos.com/embedded-dbms-gains-locking-and-cascaded-deletes/), LinuxGizmos.com.

1. ["Enea AB: Enea Protects the Communication between Database Server and Client Applications"](http://www.sectorpublishingintelligence.co.uk/news/843220/enea+ab+enea+protects+the+communication+between+database+server+and+client+applications), Regulatory news, SPi World news.

## External links

- [Official website](http://enea.com/polyhedra)

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Adapted from the Wikipedia article [Polyhedra (software)](https://en.wikipedia.org/wiki/Polyhedra_(software)) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Polyhedra_(software)?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.