执行asmca创建磁盘组没有问题，但以sqlplus / as sysasm登陆创建却出现异常
sql>create diskgroup data external redundancy disk '/dev/oracleasm/disks/*'
 *
 error at line 1:
 ora-15018: diskgroup cannot be created
ora-15031: disk specification '/dev/oracleasm/disks/*' matches no disks
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推荐阅读：
ora-01172、ora-01151错误处理 http://www.linuxidc.com/linux/2013-06/86529.htm
ora-00600 [2662]错误解决 http://www.linuxidc.com/linux/2013-06/86528.htm
ora-01078 和 lrm-00109 报错解决方法 http://www.linuxidc.com/linux/2012-07/66044.htm
ora-00471 处理方法笔记 http://www.linuxidc.com/linux/2013-09/90017.htm
ora-00314,redolog 损坏，或丢失处理方法 http://www.linuxidc.com/linux/2013-09/90646.htm
ora-00257 归档日志过大导致无法存储的解决办法 http://www.linuxidc.com/linux/2013-09/90594.htm
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解决方法
sql> show parameter asm_diskstring;
name                                type        value
 ------------------------------------ ----------- ------------------------------
 asm_diskstring                      string
sql> alter system set asm_diskstring='/dev/oracleasm/disks/*' scope=spfile;
system altered.
[root@rac1 ~]# /u01/app/11.2.0/grid/bin/crsctl stop crs
[root@rac1 ~]# /u01/app/11.2.0/grid/bin/crsctl start crs
sql> create diskgroup data external redundancy disk '/dev/oracleasm/disks/*';
diskgroup created.
以上就是ora-15031: disk specification '/dev/oracleasm/disks/*' match的内容。