Fixed Charges are created against collateral securities and these are freely identifiable but when it does not realize full amount the balance is treated as unsecured provided what was agreed in the mortgage agreement. also in the era of liquidation floating charges are crystallized ( Converted to fixed) .
Further u asked that if "Debenture holders Realize" the amount from security, less than the dues then Bankruptcy Code say the balance will be paid to them even after the unsecured creditors are settled . otherwise if the company liquidator realize the assets then they would treated as unsecured provided what is agreed as per the mortgage agreement.