The heartbeat stored procedure failed. It will be retried, but if this error continues to occur, the Lync Server service ...

The heartbeat stored procedure failed. It will be retried, but if this error continues to occur, the Lync Server service will need to be restarted.

Error code: %1 NativeError: %2
Cause: Possible issues with back-end database.
Resolution:
Ensure the back-end is functioning correctly.