Failed to connect to back-end database. Microsoft Lync Server 2010, Replica Replicator Agent will continuously attempt to ...

Failed to connect to back-end database. Microsoft Lync Server 2010, Replica Replicator Agent will continuously attempt to reconnect to the back-end.  While this condition persists, no replication will be done.

The Connection string : 
%1
Cause: Possible issues with back-end database.
Resolution:
Ensure the back-end is functioning correctly.