CxVhs
The CxVhs is the standard library for Value History Service (VHS) related objects. The VHS is a service used for archiving point data. VHS-related scripting involves the use of several types of objects:
- VhsClient Object — an interface for standard VHS scripting tasks related to reading and writing history points and values
- VhsDatastoreInterface Object — an interface for standard VHS scripting tasks related to directly creating or manipulating VHS datastores
- VhsClient Iterator Objects — interfaces for retrieving point tags from a VHS, retrieving values for a point forward and in reverse, and rolling up historical values
- VhsClient Helper Objects — interfaces for passing in requests, getting responses, storing point properties and history values, and defining history entries, statistics, history tag strings, and history values
- Enumeration Constants — interfaces for enums that can be used in script, including rollup types and rollup units.
Note: Both 32-bit and 64-bit versions of this library are available; library files are located in your CygNet source files at CygNet\Support\CxVhs.dll and CygNet\Support64\CxVhs64.dll respectively.
VHS Extensibility
A .Net API that exposes extensibility features of the CygNet Historian is available. The primary namespace, CygNet.API.Historian, allows for the storage and retrieval of extended data, including:
- the association of Blob data with historical entries
- storage of historical entry values in UTF-8
- support for an "overflow" field for historical entry values for data between 16 and 271 bytes
- support for various data types
The .Net API requires the Microsoft .NET Framework is installed, in accordance with the CygNet system requirements. See the
CygNet v9.8 System Requirements for more information.
A standalone online help file CygNet.API.chm is available for user assistance. The API libraries and help file can be found in the /Bin directory on the release image.
See VHS Extensibility for more information about extended data.
More:
