History
The repository for historical data in CygNet Software is the Value History Service, also known as the CygNet Historian or the Enterprise Historian, or simply as the VHS. History reporting is configured on a per point basis. Reporting options are properties of the point configuration record.
Both a 32-bit VHS and a 64-bit VHS are available.
Data is forwarded to the VHS by any number of CygNet Current Value Services (CVS), (most commonly the UIS, but also by the Service Monitoring Service (SVCMON), the HyperPoint Scripting Service (HSS), and the OPC Interface Service (OPCIS)) and by external CygNet clients (for example, via COM API or utility). When a CVS point’s current value changes, the new value is sent to the VHS for light processing and storage on disk.
A VHS is accessible primarily via the CygNet Explorer, although several other clients can be configured to present historicized points. Historical values for each individual point can be viewed on the History Values dialog box, which enables administrators to view a point's historical statistics, and its historical values in both a list and a time-series graph.
The topics in this section describe how history data is reported and viewed, data compression options, configuration and management of the VHS, journal files, the change queue, replication, data forwarding, quick recovery, and the several VHS utilities provided to aid in historical data management.
To address questions or circumstances beyond the scope of the CygNet Help, Additional CygNet Resources are available.
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