When making changes to your data item's URI you may see the following error:
This error means that there is already a data item that exists with the URI to which you are trying to point this page.
In this situation, select “cancel” and look through your data item list to find the associated data item. If you feel that these two items are the same thing you can go back to your changes and “confirm merge” or you can use a different # at the end of the URI to distinguish the two data items.
When you merge two data items all the fields for both will be combined into one data item. This change cannot be reverted so please do make sure this is your desired outcome.