 These relations suggest that we need extra thermodynamic cost to increase correlation (measurement case), and in contrast we can apparently violate the second law up to the consumption of correlation (feedback case).For more general information processes including biological information processing, both inequality and equality with mutual information hold.Real-life versions of Maxwellian demons occur, but all such "real demons" or Molecular demons have their entropy-lowering effects duly balanced by increase of entropy elsewhere.