A high availability database system, subject to a failure causing data corruption in the active server system, may recover valid data prior to the corruption, and use the protected and recovered data to effect a failover. At the time T1 when a stand-by computer system detects the occurrence of a failure, a pair split is done to the data area to protect the data area time T0, just before the occurrence of the failure, and another pair split is done to the log area at the time, where the log area is corrupted or a time T3, where the failover is to take effect without corrupting data, to protect the log area containing data at a given time between time TO and time T3. By using the data and log areas thus protected, the stand-by computer system may take over valid data and log areas of the given time to perform a failover.