FEATURE Smart factories and AI
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Relational versus historian database
Manufacturing companies are increasingly collecting data and it has become correspondingly more important to collect, save and distribute all stored data for further use. By George Walker, Managing Director of Novotek UK & Ireland
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any in industry use relational databases (RDBs) to increase productivity and reduce costs. Relationship databases
are built to handle and store contextual or genealogical information about the production process, but they don’t handle large amounts of time series/process data. On the other hand, historian databases collect, store and distribute large amounts of high-resolution time-series/process data, retrieving it from the local or company systems, and giving an overview of the entire production process.
Implementation
Relational databases don’t have built-in data collection capabilities, hence custom code must be written for each data source, adding to development time and costs. The lack of web-based interface means that import of tags and maintenance of the database must be done during planned downtime. By contrast, historians come with built-in data collection, which retrieve data from various sensors and systems. GE Digital’s Profi cy Historian, for example, uses the industry standards OPC and OPC UA, with data access to multiple devices. Profi cy Historian comes with pre-built interfaces, without custom coding or scripting. Data is stored and processed seamlessly in one secure, central location, for added fl exibility and cost saving.
Speed Because production operates in real time, it is important that data is received fast. Relational databases are well-suited to answer queries such as trends in data fl ows, temperatures and other analogue parameters. The challenge arises when the queries concern large data sets or longer time periods. This means that the relational database is lower performing. For faster read/write performance and continuous access to real-time data, it’s best to choose a historian database. Historians can collect large amounts of process data in milliseconds. Compared to regular relational databases, Profi cy Historian is 100-1000 times faster at reading and writing.
28 November 2023 | Automation
Compression Effi cient data storage and compression enables high performance. For a relational database, compression is done manually, through administration of archives and disk space. This is fast becoming a time- consuming job.
Historians comes with powerful features for compression. With Profi cy Historian, data is fi rst compressed on the collector, and again before storage. Archives can be automatically created, backed up and purged, enabling extended use without the need for a database administrator
Availability and redundancy It’s important that production data is always available. Relational databases off er high availability for data stored through clustering, but they are vulnerable to network availability. Depending on where the collector is located, usually on a server, or near the data source, data collection will stop if the connection is down.
Historian technology ensures good availability with redundancy at the collector. Profi cy Historian comes with Store & Forward technology, which buff ers the data at the collector if a disruption occurs. The buff ers are eventually uploaded when the server comes back online with automatic reconnection – ensuring no data loss.
Data security
Networks and databases are under constant attacks from hackers and viruses, many of which are targeted at well-known relational databases. SQL Injection/ Insertion attacks are common with RDBs. Some historians are immune to such attacks as they do not allow insert, update or deletion of data through standard interfaces. In addition, historians track all changes, including uses access, confi gurations, security violations, and system alerts. Some historians are designed to help address strict regulatory requirements such as the FDA’s CFR Part 11.
The verdict
The historian database is designed to collect amounts of data from the entire plant for process visualisation. A plant- wide historian connects both “islands” of automation data at the plant fl oor, and the plant operations up to business systems. You can compare previous production runs and analyse data before downtime, so you can easily identify trends and root causes, and implement improvements. For collecting, storing and distributing
large volumes of high-resolution process data, a historian will provide the best insights. So, relational database vs historian database? One would obviously choose a powerful historian database.
automationmagazine.co.uk
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