What Is an Array Tag?

Historian allows you to store a set of values with a single timestamp and single quality and then read the elements back individually or as an array.

On retrieval, if you specify only the tag name, then all elements are returned. If you want to retrieve only an element, you can specify <TagName>[n] where n is the element number you want to retrieve.

In an array tag:

• The size of the array tag does not need to be configured. The Data Archiver will store the number of elements that were written.
• The maximum number of elements that an array tag can store is 10000. If this limit is exceeded, Historian does not accept any further elements.
• All calculation modes except TagStats are supported by array tags. The calculation mode is applied on array elements and not on the array. For example, if you do a minimum on a three-element array, this works like three individual tags. The minimum of element [0] over time is computed and returned as the minimum of element [0]. The Data Archiver does not compute the minimum of element [0], [1], [2] at a single point in time and return that as the minimum of the array.
• When a normal tag is converted to an array tag, on data retrieval, the data of the normal tag cannot be retrieved.

You can query both an array tag and an element of the tag. Each element of the array tag will be displayed in a separate row and they all will have the same timestamp.