An approach is provided in which a standby component receives a database log record that corresponds to a modification to one of a primary database’s corresponding physical storage spaces. The rotatively hitting mechanisms are disposed in plural numbers and at plural stages in a manner concentrically to each other, and the plural rotatively hitting mechanisms are disposed in a position relationship rotationally symmetrical to each other. The display is positioned behind the viewing side of the beam-splitter so that the conferee views the display through the beamsplitter.