Data categories

AVEVA Historian is able to process and store data in a variety of ways. It categorizes each data record by type to provide a consistent framework for data operations. Each category of data has a separate set of characteristics and is handled differently by the historian.

Original versus revision data

Data acquired by AVEVA Historian can be categorized as:

• Original data is the data received from the data source originally—that is, for the first time. For example, a real-time stream of data from an I/O server represents original data. Usually the original data arrives to a Historian in high data volumes for many tags with timestamps close to each other.

• Revision data, by contrast, is data that corrects or appends original data. Revision data operations are performed on a per-tag basis and typically have far lower volumes than original data.

Streamed versus non-streamed data

Original data can be streamed or non-streamed.

• Streamed: If the data source is able to enforce time order for its output, the data is streamed data. Streamed data has three subtypes:

  • Real-time data is in time order, where the timestamp is in the past relative to the current AVEVA Historian time.

  • Late data is in time order, where the timestamp is far in the past compared to the current AVEVA Historian time.

  • Replication data is data that has been replicated from a tier-1 historian to a tier-2 historian.

• Non-streamed: If the time order is not enforced, the data is non-streamed.