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

Failed to register with 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
Exception: %2
Cause: Possible issues with back-end database.
Resolution:
Ensure the back-end is functioning correctly.