Assume that you have deleted one or more entities in Master Data Services (MDS) for Microsoft SQL Server 2012 or SQL Server 2014. When you try to edit the model security for some groups or users in MDS, you receive the following error message:
An unknown error occurred.
Note When you enable MDS trace logging and reproduce the error, the following error message is found in the trace log:
An item with the same key has already been added.
The issue occurs because the attribute level security that belongs to the deleted entity is not removed accordingly.
Each new cumulative update for SQL Server contains all the hotfixes and all the security fixes that were included with the previous cumulative update. Check out the latest cumulative updates for SQL Server:
To work around this issue, remove the corresponding attribute level security, or delete the attributes that are referenced in the group security. Then, delete the entity.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.