1. A database management method in a database management system comprising an auxiliary storage device having a storage area for storing a database therein, the method comprising the steps of: a processing request acceptor accepts a processing request as a data query; a data operation executor analyzes the accepted processing request and executing a plurality of data operations on the basis of the analyzed result; a resource manager manages the data operations allocated to generated processes or threads; and a buffer manager caches data as a target of the data operations from the auxiliary storage device into a memory upon execution of the data operations and determines whether or not the data as the data operation target is present in the cache, and wherein the buffer manager determines whether or not the data is present in the cache when the data operation executor executes the data operations; the resource manager determines the usable state of the processes or threads in the data operations when the data is not present in the cache; the resource manager sends an access request of caching data as the target of the executed data operations in the memory to the auxiliary storage device in order to execute the data operations through the processes or threads when some of the processes or threads are free or usable; the resource manager, when all the processes or threads are already used, executes the data operations after some of the processes or threads are released or free; and in the presence of the data in the cache, the resource manager executes the data operations.