A data processing system may include: a memory system suitable for sorting a plurality of index data having a tree structure wherein each index data comprises information indicating a tree level thereof into a plurality of groups through a first and second sorting operations, the first sorting operation comprising sorting the index data based on their respective tree level information, the second sorting operation comprising sorting the index data based on the numbers of accesses to their respective index data, saving the groups into different storage regions; and a host suitable for managing a plurality of index data into said tree structure.