由于oracle数据库服务器异常掉电、人为误操作、oracle数据库bug等原因，造成oracle磁盘组无法mount，oracle数据库无法open,存储在asm中的数据面临丢失的风险，如果asm磁盘file1(filedirectory)信息及data数据块未被破坏，可以使用增强版asmcmd进行恢复，详细过程如下所示。2.环境准备

ddif=/dev/zeroof=/dev/oracleasm/disks/arch1bs=1Mcount=2conv=notruncddif=/dev/zeroof=/dev/oracleasm/disks/arch2bs=1Mcount=2conv=notruncddif=/dev/zeroof=/dev/oracleasm/disks/arch3bs=1Mcount=2conv=notruncddif=/dev/zeroof=/dev/oracleasm/disks/arch4bs=1Mcount=2conv=notruncddif=/dev/zeroof=/dev/oracleasm/disks/arch5bs=1Mcount=2conv=notrunccreatediskgroupdata01externalredundancydisk/dev/oracleasm/disks/arch1,/dev/oracleasm/disks/arch2,/dev/oracleasm/disks/arch3,/dev/oracleasm/disks/arch4,/dev/oracleasm/disks/arch5attribute