Some objects in a mapping are also stored as independent objects in the repository:

The mapping is dependent on these objects. When this metadata changes, the Designer and other PowerCenter Client applications track the effects of these changes on mappings. In these cases, you may find that mappings become invalid even though you do not edit the mapping. When a mapping becomes invalid, the Integration Service cannot run it properly, and the Workflow Manager invalidates the session.

The only objects in a mapping that are not stored as independent repository objects are the non-reusable transformations that you build within the mapping. These non-reusable transformations are stored within the mapping only.