A method for operating a data processing system including a host and a memory system coupled to each other through a plurality of slots and using a Universal Flash Storage (UFS) interface, the method includes: allocating, by the host, dedicated memory regions respectively corresponding to the slots during a booting operation of the host; communicating, between the host and the memory system in parallel through the slots based on command packets and address information for data buffer regions, the command packets and the address information being stored in the dedicated memory regions; and deallocating, by the host, the dedicated memory regions during a shutdown of the host.