# Performance considerations when using extended tag properties

ControlLogix extended tag properties provide application efficiencies and high integration between the control and HMI application programs. Before undertaking the design of an HMI application accessing extended tag properties, an HMI designer needs to consider the performance characteristics related to extended tag properties.

Extended tag properties are integrated into the ControlLogix application program. On a controller, the metadata is stored in FLASH memory. To maintain controller performance, the system design requires each extended tag property that is used on an HMI display be accessed separately. This design affects the display loading time within the HMI application. When loading a display that uses extended tag properties, all objects (for example, numeric display, button captions, and the like) will be wire-framed before all data and extended tag property data is read from the controller.

The time to load the extended tag property data depends on how many extended tag properties are used on a display. To improve overall HMI application performance, extended tag property data is cached in memory. This caching improves the display loading performance when a display is revisited.

Extended tag properties can be used with the runtime language switching feature of FactoryTalk View. When a language switch occurs, the HMI application will read, if the locale exists, the referenced string-type extended tag property values, for example, .@Description. Reading the extended tag property values delays the display refresh that occurs when a language switch occurs. The refresh delay is the same as the delay when a display is initially loaded.

The following tables show the performance data that was generated using an Allen-Bradley 1756-L75 controller running V28 firmware and an Allen-Bradley 1756-L85 controller running V28 firmware. You can use the data as a reference to estimate the impact to your applications that use extended tag properties.

## See also

About controller tag extended properties

Memory considerations when using extended tag properties