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.