Abstract: A method for producing a duplication of a database stored in an external storage by writing over copy data of the database with update log data which was acquired after acquisition of the copy data. This method is implemented in a computer system having a virtual storage operating system. The system includes a virtual storage area which is defined as having virtual pages which have a one-to-one correspondence to blocks in an external copy data storage, where the virtual pages are the database copy data is stored and in an order according to physical addresses of the blocks. Each update log data is acquired in units of the blocks. A control table is provided which includes control values which have a one-to-one correspondence to the virtual pages. A control value from the control table is set when the update log data is set to the virtual pages.

Abstract: In an online system having processors which execute a plurality of online jobs, a standby processor is provided along with a wait job which is executed by this processor and which has organization information of a logical sum of organization information items of the plurality of online jobs. When a failure has occurred as to any of the online jobs, only the organization information item of the failed online job within the organization information of the wait job is left valid. Thereafter, a process of the failed online job is switched to and executed by the wait job.