A computer system including a copy source volume and a copy target volume which may be selectably PAIRED or SPLIT. 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. 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. PAIR management information stores the PAIR status and the BACKUP ENABLED or DISABLED status.