at least one storage having one or more volumes configured to serve as a storage region, including a copy source volume and a copy target volume which may be selectably PAIRED or SPLIT;

a managing computer for managing the storage, and including user management information, operation management information and PAIR management information, where:

the user management information stores:

an entry indicating that a first user is permitted to effect a PAIR operation and a PATH operation; and,

an entry indicating that a second user is permitted to effect a PATH operation;

the operation management information indicates permitted PATH and PAIR operations in relation to each user and a volume's PAIR or SPLIT status, and stores:

an entry indicating that the first user is permitted to effect the PAIR operation in which the PAIR status is PAIR, or is SPLIT WITH BACKUP DISABLED; and,

an entry indicating that the second user is permitted to effect the PATH operations in which the PAIR status is SPLIT WITH BACKUP ENABLED; and,

the PAIR management information stores the PAIR status and the BACKUP ENABLED or DISABLED status; and

a plurality of host computers including a first host computer and a second host computer, each host computer being used by a user capable of obtaining an operation authority over a volume in the storage, where the storage, the managing computer, and the host computers being interconnected via a network, and two or more users being capable of concurrently having the operation authority for an identical volume;

the method carried out by the managing computer and configured, wherein if a current status is the PAIR status, to effect operations upon:

A) receiving a first request from the second user to enable access of the copy target volume by the second host computer identified, of deciding that the first request is not allowed based on the user management information, the operation management information and the PAIR management information, and sending an error message;

B) receiving a second request from the first user to change a status from the PAIR WITH BACKUP ENABLED to SPLIT, of deciding that the second request is allowed based on the user management information, the operation management information and the PAIR management information, and sending a PAIR SPLIT request to the storage apparatus;

C) receiving a third request from the first user to resynchronize to the PAIR status, of deciding that the third request is not allowed based on the user management information, the operation management information and the PAIR management information, and sending an error message; and,

D) receiving the first request after completion of B), of deciding that the second request is allowed based on the user management information, the operation management information and the PAIR management information, and sending a PATH creation request to the storage apparatus.