About the Historian Server

The Historian server is the central point for managing all of the client and collector interfaces, storing data and (optionally) compressing and retrieving data.

In the Historian server, data is stored in files called data archives. These files contain all the tag data gathered during a specific period of time (for example, time-based archives such as daily archives). They have the .iha extension.

You can store data of various data types such as Float, Integer, String, Byte, Boolean, Scaled, and binary large object data type (BLOB). The source of the data defines the ability of Historian to collect specific data types. If you have the license to store the alarms and events data, the server also manages the storage and retrieval of OPC Alarms and Events in a SQL Server Express.

You can further segregate your tags and archives into data stores. A data store is a logical collection of tags used to store, organize, and manage tags according to the data source and storage requirements. A data store can have multiple data archives, and includes logical and physical storage definitions.

The primary use of data stores is segregating tags by data collection intervals. For example, you can put name plate or static tags where the value rarely changes in one data store, and put process tags in another data store. This can improve the query performance.

The Historian Data Archiver is a service that indexes all the data by tag name and timestamp and stores the result in an .iha file. The tag name is a unique identifier for a tag (which is a specific measurement attribute). For iFIX users, a Historian tag name normally represents a Node.Tag.Field (NTF). Searching by the tag name and time range is a common and convenient way to retrieve data from Historian. If you use this technique to retrieve data from the archive files, you need not know which archive file contains the data. You can also retrieve data using a filter tag.

The Historian server performs the following tasks:
  • Manages all system configuration information.
  • Manages system security, audit trails, and messaging.
  • Services write and read requests from distributed clients.
  • Performs final data compression.
  • Manages archive files.