Abstract: A method of matching the operations of a primary computer and a backup computer for providing a substitute in the event of a failure of the primary computer is described. The method comprises assigning a unique sequence number to each of a plurality of requests in the order in which the requests are received and are to be executed on the primary computer, transferring the unique sequence numbers to the backup computer, and using the unique sequence numbers to order corresponding ones of the same plurality of requests also received at the backup computer such that the requests can be executed on the second computer in the same order as that on the first computer. In this manner, the status of the primary and backup computers can be matched in real-time so that, if the primary computer fails, the backup computer can immediately take the place of the primary computer.