A method is provided to handle portable cassettes removeably disposed in a data storage library, wherein the method supplies a data storage library comprising a plurality of storage slots, and a plurality of portable cassettes removeably disposed a designated storage slot in a first alignment order, and a pass-through accessor comprising a moveable fixturing apparatus to store portable cassettes, wherein the pass-through accessor is moveably disposed in the data storage library. The method positions the pass-through accessor adjacent an open end of a designated storage slot, and sequentially removes and attaches to the fixturing apparatus a plurality of portable cassettes from the designated storage slot. The method then transports the plurality of portable cassettes to a designated location within the data storage library.