| 摘要 |
PURPOSE:To prevent recurrence of an error in advance by assigning a control data storage area not in use if an error occurs in accessing a control data storage area to ensure the restoration of failed subchannel. CONSTITUTION:It is supposed that an error occurs when a control program accesses a control data storage area SCWA1 of an address B1. A control program detecting it is informed it to a CPU immediately. The CPU receiving the information searches a subchannel not in use, and when supposing that the n-th subchannel, for example, is not in use, then sinc an SCWAn of an address Bn is used, the CPU gives a command to a transfer device that the content of an address A1 of a memory 4' is rewritten into the Bn. The control program rewrites the content of the address A1 of the memory 4' into the Bn (address of the SCWAn) as shown in (b). Further, the subchannel No.1 is controlled by using a control data written in the SCWAn.
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