the second product is in the form of multi-class mbs with credit-enhancement provided through segmentation of the issue into senior and junior tranches commonly known as collateralized mortgage obligation or cmo, over-collateralization or reserve fund arrangements 第二類是多級別按揭證券信貸增方法包括拆分證券為高級及次級通稱為抵押按揭權(quán)責(zé),預(yù)留資金,超額抵押及上述組合等。