| 摘要 |
PURPOSE:To eliminate the need of writing back the corresponding block to a block managing part at the time of drawback by providing a drawback processing means for bringing data stored in a first external storage medium to drawback to a second external storage medium. CONSTITUTION:A first counter 15 in a file managing part 17 is operated and brought to increment only at the time of total drawback and incremental drawback, a second counter 16 is operated only at the time of total drawback and set to the same value as that of a first counter, and a third counter 20 in a black managing part 21 is operated only at the time of updating of real data 19 in the corresponding block 18 and set to the same value as that of a first counter 15. Accordingly, without providing an updating flag on the block managing part 21 of each block 18 in a file 12, a reference time point as to whether the block is updated due to a difference of a drawback system or not becomes clear. In such a way, it becomes unnecessary to write back the corresponding block to the block managing part at the time of total drawback and incremental drawback.
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