1. A database server, comprising: a plurality of cache memory managers; a shared memory manager which divides a shared memory into a plurality of memory chunks to manage the shared memory and allocates at least one memory chunk to each of the plurality of cache memory managers based on a request of each of the plurality of cache memory managers; wherein each of the plurality of cache memory managers requests at least one of the plurality of memory chunks to the shared memory manager, wherein the database server uses at least one of the memory chunks which are allocated to each of the plurality of cache memory managers as a cache memory having a predetermined purpose, and the predetermined purpose of each of the plurality of cache memory managers are different from each other, and wherein each of the plurality of cache memory managers determines to delete at least a part of the data stored in a cache memory managed by each of the plurality of cache memory managers based on a size of the shared memory and a memory size allocated to the plurality of cache memory managers, before determining whether to request at least one memory chunk to the shared memory manager; and a main processor which performs a database operation using a cache memory.