If a user requests change (or deletion) of a stored data item that is not currently being displayed, both the old and new values should be displayed so that the user can confirm or nullify the change before the transaction is completed.
Additional Information:
For proposed deletion of significant amounts of data, such as entire files, it probably will not be feasible to display all of the data. In such instances, sufficient information should be provided so that users can identify those files they have selected for deletion. The user should be clearly advised of the potential data loss and required to confirm the destructive action before it will be executed. This practice will tend to prevent inadvertent change, including changes resulting in loss of needed data. User attempts at selective data change without displayed feedback will be prone to error.