| 摘要 |
PROBLEM TO BE SOLVED: To permit data migration between old and new systems without shutdown. SOLUTION: A plurality of first access routes 20, 21 from a CPU 10 to an old CU 13 (old subsystem) having an old VOL 14 under its control are prepared, and, between the old CU 13 and a new CU 11 (new subsystem) having a new VOL 12 under its control, a plurality of third access routes 30, 31 are set. Then, by splitting over more than once, connections are changed from the first access routes 20, 21 of the old subsystem of transmission source to the second access routes 20', 21' of the new subsystem of transmission destination. During the connection change, if the new subsystem receives an access from the CPU 10 through the second access routes 20', 21' of the new subsystem side, a path migration control part 111 relays the access, through the third access routes 30, 31, to the old subsystem side, where the access is processed. The data migration from the old subsystem to new one is executed after all the first access routes are switched to the second access routes.
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