SYSTEM FOR RE-FORMATTING MAGNETIC DISK IN OPERATING

PURPOSE:To realize the re-formatting of a magnetic disk in operating by limiting a track range to be re-formatted in one processing, and suppressing only the input/output of a user program which makes access within the range. CONSTITUTION:The re-formatting of the magnetic disk is performed at every re-formatting part 1a when a track group is divided into plural re-formatting part 1a, and information with respect to in which range of track is targeted as the re-formatting at present is stored in a re-formatting information storage table, and only the user program which desires to perform input/output to the range is held by a pending means 4, and the input/output from the user program for which no re-formatting is performed at present on another track is permitted. Also, by trying to make access to the track range in processing the re- formatting, an input/output request held at the pending means 4 is released from pending after the re-formatting of the track range is completed by a releasing means 7. In such a way, it is not required to stop the use of the magnetic disk for the user program.