Tag value retention

The detail portion of the Tagname Dictionary includes two properties to retain tag values and operator changes to alarm limits.

All tag types include a Retentive Value property. Select Retentive Value to retain the current value of the tag when the application stops. When you start the application again, WindowViewer uses the retained value as the initial value of the tag.

WindowViewer does not write retained values to I/O devices when WindowViewer starts the application again. I/O values are updated after the I/O Server initially scans the device providing data.

The Retentive Value option cannot be selected or cleared for new or existing tags if WindowViewer is running. When you select this option, the initial value of the tag is constantly updated to reflect its current value. When WindowViewer stops, the initial value is set to the last retained value. If this option is later cleared, the initial value of the tag is set to the last retained value.

Integer and real tags include the Retentive Parameters property. Select Retentive Parameters to retain any changes made by the operator to a tag’s alarm limit while the application is running. WindowViewer uses the modified alarm limit as the initial value for the alarm limit when the application is restarted.