Patent ID: 7039660

Claim:
A method for updating primary and secondary log blocks stored in primary and secondary disk subsystems of primary and secondary database processing systems, respectively, in order to be ready for disaster recovery at an occurrence of a failure in the primary database processing system, the method comprising the steps of: receiving, by the primary disk subsystem, a write command from a primary host computer via a network; writing, by the primary disk subsystem, data indicated by the write command thus received into a cache of the primary disk subsystem; determining, by the primary disk subsystem, whether the received write command is a command to write data into the primary log block; transferring, from the primary disk subsystem, the received write command to the secondary disk subsystem via the network, if the received write command is a command to write data into the primary log block; tracing, by the primary disk subsystem, log records constituting the primary log block stored in the primary disk subsystem to update data of a primary database in the primary disk subsystem; reporting, by the primary disk subsystem, completion of write operation of the data indicted by the received write command to the primary host computer via the network; receiving, by the secondary disk subsystem, the write command transferred from the primary disk subsystem via the network; writing, by the secondary disk subsystem, the data indicated by the write command thus transferred into a cache of the secondary disk subsystem; determining, by the secondary disk subsystem, whether the transferred write command is a command to write data into the secondary log block; and tracing, by the secondary disk subsystem, log records constituting the secondary log block stored in the secondary disk subsystem to update data of a secondary database in the secondary disk subsystem, when the transferred write command is a command to write the data into the secondary log block.