Every time a domain value map is opened in an edit session, a sandbox is created per domain value map, per user. If you save your changes, then the changes are saved in your sandbox.

You must publish the changes you make to have them picked up by the runtime and be saved permanently to the MDS repository. In a session, you can also save your changes without publishing them. In such a case, the domain value map remains in the saved state. You can reopen the domain value map and publish the changes later.