Diagnosis
You tried to delete an entry that was only filled in the field'System'. The field 'Profile' or 'Activity group' was empty. Theseentries document that although the user is distributed in the system,he or she does not receive any assigned profiles or activity groups.

System Response
The entry was not deleted.

Procedure
If you want to prevent distribution in this system, you must remove thesystem using the tab 'System'.