The changes you requested to the table were not successful because they would create duplicate values in the index, primary key or relationship

Error Message

When performing any of these tasks:
- Copy/Paste in ArcCatalog.
- Start editing within ArcMap.
- Editing features in a geodatabase through the ArcMap Editor.
- Adding an index to a field.

A variation on the following error message is raised:

"The changes you requested to the table were not successful because they would create duplicate values in the index, primary key or relationship. Change the data in the field or fields that contain duplicate data, remove the index or redefine the index to permit duplicate entires and try again."

Cause

As the message indicates, there are duplicate values in an index, primary key or relationship in a table or feature class.

Solution or Workaround

1. The error may be due to a user-generated unique index. Confirm that no such indexes exist. If they do, delete the index before proceeding.
2. If the error is generated while adding an index to a field, confirm that the field in question does not have any duplicate values. If it does, they need to be removed before the index can be added.
3. If the error is raised during editing, the issue describe in the following knowledge base article may be what is being encountered:
   
   Article 23687 - Error: The changes you requested to the table were not successful
   
   Follow the steps in article 23687 to resolve the issue.