Advanced Historian Topics
For an overview of the Historian Module, including definition of key concepts, visit Historian, Time Series Data.
On this page:
Archiving Process Overview
The Historian module has a three-step archiving process:
An event triggers the request to archive a group of values. There are two types of events (Trigger or TagChange), which are configured in a Historian Table.
The Historian archives the values in the Target database. The Target Database can be a SQL Database or a TagProvider that is configured to act as a historian.
If Store and Forward is enabled, the data synchronization is executed. This option stores data in a local database if the Target Database is not available, and sends it to the target when it becomes available.
The archiving process considers two types of archiving events:
Trigger: The Trigger can be a Tag Value, Tag Property, or any object from the runtime namespace (e.g., server.minute). When a value change is detected in the object, the archive request event is generated. Only Tags of domain Server or objects residing in server-side namespaces can be used as Triggers since the Historian process runs on the Server computer. The Trigger is configured in the HistorianTable. All tags and objects connected to that HistorianTable will be requested to be archived, regardless of having or not a new value.
Tag Change: The Tag Change is a check-box on the TableHistorian configuration. Enabling this checkbox allows the Historian process to verify all tags connected to that HistorianTable. When the tag has a new value, the archive request event is generated. The request to archive will be generated only for the Tag that has a new value. However, according to the Historian Target Database, only the tag or all tags in the group will be archived. Further information on this is included in the next section of this page.
For a more detailed Historian execution explanation, check Archiving process.
Historian Runtime Attributes
The Historian namespace exposes properties and methods of the .NET objects used by the Tag Historian Module execution.
For general information on namespace and object concepts, go to the section Objects and Namespaces.
This section describes only some commonly used properties. See Namespaces Reference for the complete list of properties and available methods.
Examples of Historian properties | |||
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Property | Type | Description | To access the property on CodeBehind |
| Boolean | This is a Boolean flag that indicates whether the Module Historian has started. If the flag is set to "true," it means that the Module Historian is up and running, actively archiving data according to the configured Historian Tables. If the flag is set to "false," the Module Historian has not yet started, and no data archiving is taking place. |
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| String | This is a string that displays a message indicating the success or failure when initiating the Module Historian. If the Module Historian starts successfully, the message will typically show "OK" or a similar confirmation. If there is an error during the initiation process, the message will display an error description to help diagnose and troubleshoot the issue. |
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| Boolean | This is a Boolean flag that, when enabled, allows the creation of temporary binary files on the server computer to optimize the performance of the TrendChart object when requesting large amounts of data. With caching enabled, the system can quickly retrieve the necessary data for the TrendChart object without causing significant delays or performance issues. By setting this flag to "true," users can benefit from improved performance and responsiveness when working with large datasets in the TrendChart object. |
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In this section: