COMPUTER SYSTEM AND DETECTING METHOD FOR DETECTING A SIGN OF FAILURE OF THE COMPUTER SYSTEM

A service AP conducting ordinary business processing is executed on a first OS. The first OS includes an operation recording controller for recording operation conducted by the first OS as operation recording information together with time when the operation is conducted, and an auxiliary driver for accepting and executing external processing. A multi-OS controller interface included in a second OS, which is higher in reliability than the first OS, operates a multi-OS controller from an AP operating on the second OS. An analysis and prediction AP operating on the second OS analyzes states of the first OS and the service AP, and detects a failure sign. Upon detecting a failure sign, degrade operation of the OS or service AP to be analyzed, preparations for switching from an active system to a stand-by system, and actual switching are conducted before the failure occurs.