| 摘要 |
PURPOSE:To prevent duplicated magnetic disk devices DK from being simultaneously damaged by temporarily suspending the execution of a channel program or restarting the temporarily suspended channel program under control based on a CPU. CONSTITUTION:When an operation restarting instruction RIO operation is received from a CPU 2, '1' is added to the contents of a counter 33. The CPU 2 successively reads out prepared channel programs, and when a read command control word CCW is a HALT command, the execution of the RIO operation is waited when the contents of the counter 33 are '0'. When the RIO operation is executed and the contents of the counter 33 are turned to '1' (namely when the CPU 2 generates the RIO operation after reading out the HALT command), '1' is subtracted from the contents of the counter 33, a CCW to be executed next to the current CCW is read out, and when the contents of the counter 33 are >='1', '1' is subtracted immediately from the contents of the counter 33, a CCW to be executed next to the current CCW is read out. Consequently, the duplicated DKs can be prevented from being simultaneously damaged. |
