ORA-15206: duplicate diskgroup string specified
Cause: A command specified the same diskgroup twice.
Action: Specify each diskgroup only once.
ORA-15206的错误消息代表重复的磁盘组字符串被指定，官方解释是：
ORA-15206: duplicate diskgroup string specified
Cause: An attempt was made to add the same disk group to Oracle Automatic Storage Management (ASM) more than once in the same ALTER DISKGROUP statement or in separate ALTER DISKGROUP statements.
Action: Specify each disk group once. If multiple instances of the same disk group need to be added to ASM at the same time, specify the number of new disk groups to add in the DISK_REPAIR_TIME parameters.