Abstract: Any one of a first storage area and a second storage area, in which redundant data are respectively written, is set as a reference storage area, reference data are read in accordance with a request from the storage area set as the reference storage area between the first storage area and the second storage area, and, when update data are received from an external storage device, information based on the update data is written in the storage area not set as the reference storage area between the first storage area and the second storage area and the information based on the update data is written in the storage area set as the reference storage area.

Abstract: A database system is formed by connecting node devices in parent-child relations. Each of the node devices includes a data storing unit, a saving rule storing unit, a storage processing unit, and an inquiry processing unit. The saving rule storing unit stores a saving rule used for saving data stored in the data storing unit to a parent node device in a case in which its own node device is not a parent of a highest rank and deleting the data in a case in which its own node device is the parent of the highest rank. The storage processing unit writes data and saves data to be saved from the data storing unit into a parent node in an order represented by order information associated with the data or deletes data to be deleted by referring to the saving rule.

Abstract: Any one of a first storage area and a second storage area, in which redundant data are respectively written, is set as a reference storage area, reference data are read in accordance with a request from the storage area set as the reference storage area between the first storage area and the second storage area, and, when update data are received from an external storage device, information based on the update data is written in the storage area not set as the reference storage area between the first storage area and the second storage area and the information based on the update data is written in the storage area set as the reference storage area.

Abstract: The first DS in accordance of the inquiry from the integration server, extract first data from the first DB and generate a first hash value based on the first data. The second DS in accordance of the inquiry from the integration server, extract second data from the second DB and generate a second hash value based on the second data. The first DS transmits the first hash value to the second DS. The second DS collates the first hash value with the second hash value, transmits, to the integration server, a collation result and at least a part of the second data, for which the first hash value and the second hash value are matched, and transmits a matched part of hash values to the first DS. The first DS transmits at least a part of the first data that was a source of the matched part of hash values to the integration server. The integration server combines the data received from the first DS and the second DS on the basis of the collation result.

Abstract: According to one embodiment, a DB integration device includes a receiver and a designator. The receiver is configured to receive at least a request for combining first data and second data. The designator is configured to designate, from among a plurality of DB systems, a DB system for executing a combining process of combining the first data and the second data on the basis of combining capability information. The combining capability information indicates at least one of: whether or not a first DB system is capable of reading the second data from a second DB system and executing the combining process; and whether or not the first DB system is capable of causing the second DB system to read the first data.