| 摘要 |
PURPOSE:To improve the reliability of update control information and lighten the load on an external controller by indicating whether the update control function of a dual file is effective or not, and eliminating the acquisition of the update control information when it is not necessary. CONSTITUTION:A command from a controller 14 is decoded by a high rank interface circuit 27, and when the command is concerned in writing operation, a prescribed address in an update control area 18a is accessed by an address pointer 28 to write data by a writing circuit 30. When the command is concerned in reading operation, data is read out by a reading circuit 29. Ports of disks 22 and 24 and adapters 18 and 20 to controllers 14 and 16 are written by the devices and channels in update control areas 18a and 20a to obtain a processing history. The history consists of a data significance flag, update start date, update start block address, update end block address, and data check flag. |
