PURPOSE: To automate a double storage of a data by referring to a backup table by a sub-job for operating in the course of a holding mode of a main job which has been started, and writing the data block concerned of a user data file to a backup data file.

CONSTITUTION: While amain job 1 is processing a user data in an execution mode, a block which necessitates a double storage in a user data is registered in a backup table 3 by a flat, etc. On the other hand, by setting so that a sub- job 2 starts to operate as soon as the main job 1 becomes a holding mode, whenever the execution of the main job 1 becomes a pause for the present, the data block concerned of a user data file 4 is written to a backup data file 5 by the sub-job 2. In this way, a double storage of the user data without troubling an operator's operating consciousness, and also, without considering especially an application program, and without decreasing a processing speed of a machine.