Diagnosis
Settings in Customizing (Document management -> Control data ->Document link) determine that documents of type &V1& can only be linkedto this object on a 1:n basis.
This means, for example. that only one material can be assignedto a document of type &V1&. However, the same document can be assignedto a number of other materials.
As this object is already assigned to another document of document typeV1, the document cannot be assigned.

Procedure

• To find out which document of document type &V1& is already assigned to
the object, choose function Document -> Search.
If you are creating the assignment from the object (for example,material), you see the document displayed in a list.

• Decide which document is the one you want to assign the object to.

If appropriate, delete an existing assignment and enter the new one.