之前RAC环境出现了故障，节点2操作系统崩溃，重装系统后，CRS添加成功，但是CRS启动有问题，排查发现节点2 ASM的+DATA diskgroup无法mount，报如下错误：
ORA-15063: ASM discovered an insufficient number of disks for diskgroup "DATA"
在ASM实例上检查磁盘组和磁盘的状态，发现+DATA diskgroup的6块盘有3块是MEMBER，有3块是PROVISIONED。
NOMOUNT状态，导致添加操作失败，而尝试在目前正常工作的节点添加磁盘，结果同样报错：

1. SQL> alter diskgroup DATA add disk '/dev/oracleasm/disks/OADB_DATA_300G_6';
   
2. alter diskgroup DATA add disk '/dev/oracleasm/disks/OADB_DATA_300G_6'
   
3. *
   
4. ERROR at line 1:
   
5. ORA-15032: not all alterations performed
   
6. ORA-15029: disk '/dev/oracleasm/disks/OADB_DATA_300G_6' is already mounted by this instance

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