数据库实例日志：
Tue Mar 01 12:18:12
SUCCESS: diskgroup ORADISKGRP1 was dismounted
SUCCESS: diskgroup ORADISKGRP1 was dismounted
Errors in file C:\APP\ORACLE\PRODUCT\11.2.0\diag\rdbms\bflex\bflex1\trace\bflex1_ckpt_6376.trc:
ORA-00206: error in writing (block 3, # blocks 1) of control file
ORA-00202: control file: '+ORADISKGRP1/bflex/controlfile/current.287.925642037'
ORA-15078: ASM diskgroup was forcibly dismounted
ORA-15078: ASM diskgroup was forcibly dismounted
再看asm日志
Tue Mar 01 12:18:12
ASM Health Checker found 1 new failures
Dirty Detach Reconfiguration complete
Tue Nov 01 12:18:12
WARNING: dirty detached from domain 1
NOTE: cache dismounted group 1/0x5DD073B7 (ORADISKGRP1)
SQL> alter diskgroup ORADISKGRP1 dismount force /* ASM SERVER:1573942199 */
Tue Nov 01 12:18:12
NOTE: cache deleting context for group ORADISKGRP1 1/0x5dd073b7
GMON dismounting group 1 at 6 for pid 30, osid 7684
NOTE: Disk ORADISKGRP1_0000 in mode 0x7f marked for de-assignment
NOTE: Disk ORADISKGRP1_0001 in mode 0x7f marked for de-assignment
NOTE: Disk ORADISKGRP1_0002 in mode 0x7f marked for de-assignment
SUCCESS: diskgroup ORADISKGRP1 was dismounted
SUCCESS: alter diskgroup ORADISKGRP1 dismount force /* ASM SERVER:1573942199 */
SUCCESS: ASM-initiated MANDATORY DISMOUNT of group ORADISKGRP1
这里的asm日志很明显由于asm disk无法正常访问,报ORA-27072错误,磁盘组被强制dismount. 一般出现这样故障的原因大多都是人为误操作造成的，比如挂到A机的裸盘被挂至B机，然后被误格式化。
处理办法：
先用kfed恢复磁盘头
使用asmtool -list查看相关磁盘信息
然后用dbv检测是否有坏块，没有就好办了。幸好asm有备份，用备份恢复即可。
