# Memory considerations when using extended tag properties

The HMI system caches extended tag property values to improve performance. The HMI system caches extended tag property values for each runtime language viewed while the HMI application is executing. The cache is stored in RAM. On PanelView Plus 6 and PanelView Plus 7 terminals, there is a limited amount of RAM. To prevent the PanelView Plus 6 or PanelView Plus 7 terminal from encountering an out-of-memory condition, the system is designed to empty the extended tag property cache after eight hours. The system will remove all cached extended tag property values from the RAM cache except for the value associated with the HMI default language and the last runtime language viewed.

## Example

Assume an HMI application supports English (default language), French, and Chinese languages. When the application is launched, the English language extended tag property values will be read and cached as the operator navigates to different displays. After four hours of operation, the operator switches to French. After two additional hours of operation in French, the operator switches to Chinese. If nothing else changes, after eight hours passes, the French language extended tag property values will be removed from the cache. The English language and Chinese language extended tag property values will be retained in the cache.

## See also

About controller tag extended properties

Performance considerations when using extended tag properties