A second query execution part is added to a database management system comprising a first query execution part configured to execute a query based on a query execution plan of a query to a database and to return a query execution result to the query issuance source and a buffer management part configured to read a data of a read request from the database to store the data into the buffer and to provide the data to an issuance source of the read request if data of a read request has not been stored in a buffer in the case where the read request of data is received and configured to read data of a read request from the buffer and to provide the data to a issuance source of the read request if data of a read request has been stored in the buffer. The second query execution part executes the query based on the query execution plan and issues a read request of necessary data to the buffer management part for a query execution procedure. By this configuration, in the case where a first query execution part issues a read request of data, the data has already stored in the buffer in some cases.
