The stored procedure for doing intra/inter pool migration failed. It will be retried, but if this error continues to occur, ...

The stored procedure for doing intra/inter pool migration 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.