Certain files may only need to be deployed when the application is first installed and should not be modified when the application is updated. For example, a data file containing some initial data that will be modified by the application itself should not be overwritten with the original data when the application is updated. Files marked Only on first install in the deployment package that already exist on the mobile device will not be modified on the mobile device when the application is updated.
To mark a file as Only on first install, right-click on the file in the files tree and select Only on first install in the context menu so that it is checked. To clear the Only on first install setting, right-click on the file and select Only on first install a second time to remove the check mark.