Malfunction: PeoplePicker of the SharePoint farm is not working

Currently the PeoplePicker of the SharePoint farm is not available. At the moment is it not possible to add users to a group or share documents with new users. The existing permissions are not affected.
 
This affects the entire GWDG farm, so all site collections that begin with the following path:
 
·         sharepoint.mpg.de/…
·         sharepoint.uni-goettingen.de/…
·         sharepoint.gwdg.de/…
·         Wiki.uni-goettingen.de/…
 
 
The problem will be resolved as quickly as possible.