接到客户恢复case请求，希望我们接入恢复数据。大概过程是这样的，16年9月份由于硬件问题，导致normal磁盘组(只有2个磁盘)中的一个磁盘丢失，然后在17年3月6日，运维方尝试增加该磁盘进入磁盘组，结果通过force命令加入成功之后，磁盘组dismount，然后再也无法mount成功。
磁盘组创建信息

Fri Jun 24 19:31:38 2016
NOTE: Instance updated compatible.asm to 11.2.0.0.0 for grp 2
SUCCESS: diskgroup DATADG was mounted
SUCCESS: CREATE DISKGROUP DATADG NORMAL REDUNDANCY  DISK '/dev/asm-diskdata01' SIZE 1048576M ,
'/dev/asm-diskdata02' SIZE 1048576M  ATTRIBUTE 'compatible.asm'='11.2.0.0.0','au_size'='4M' /* ASMCA */

这里可以看出来datadg是一个normal的au为4M的一个磁盘组

自动drop异常asm disk

Mon Sep 12 11:41:54 2016
WARNING: Waited 15 secs for write IO to PST disk 1 in group 1.
WARNING: Waited 15 secs for write IO to PST disk 1 in group 1.
Mon Sep 12 11:41:55 2016
NOTE: process _b000_+asm1 (19491) initiating offline of disk 1.3915923833 (DATADG_0001) with mask 0x7e in group 1
NOTE: checking PST: grp = 1
GMON checking disk modes for group 1 at 9 for pid 29, osid 19491
NOTE: group DATADG: updated PST location: disk 0000 (PST copy 0)
NOTE: checking PST for grp 1 done.
NOTE: sending set offline flag message 2870990318 to 1 disk(s) in group 1
WARNING: Disk DATADG_0001 in mode 0x7f is now being offlined
NOTE: initiating PST update: grp = 1, dsk = 1/0xe9684179, mask = 0x6a, op = clear
GMON updating disk modes for group 1 at 10 for pid 29, osid 19491
NOTE: group DATADG: updated PST location: disk 0000 (PST copy 0)
NOTE: group DATADG: updated PST location: disk 0000 (PST copy 0)
NOTE: PST update grp = 1 completed successfully
NOTE: initiating PST update: grp = 1, dsk = 1/0xe9684179, mask = 0x7e, op = clear
GMON updating disk modes for group 1 at 11 for pid 29, osid 19491
NOTE: group DATADG: updated PST location: disk 0000 (PST copy 0)
NOTE: group DATADG: updated PST location: disk 0000 (PST copy 0)
NOTE: cache closing disk 1 of grp 1: DATADG_0001
NOTE: PST update grp = 1 completed successfully
Mon Sep 12 11:42:55 2016
WARNING: Waited 15 secs for write IO to PST disk 0 in group 1.
Mon Sep 12 11:44:58 2016
WARNING: PST-initiated drop of 1 disk(s) in group 1(.1137226115))
SQL> alter diskgroup DATADG drop disk DATADG_0001 force /* ASM SERVER */
NOTE: GroupBlock outside rolling migration privileged region
NOTE: requesting all-instance membership refresh for group=1
Mon Sep 12 11:44:59 2016
GMON updating for reconfiguration, group 1 at 12 for pid 29, osid 19491
NOTE: cache closing disk 1 of grp 1: (not open) DATADG_0001
NOTE: group DATADG: updated PST location: disk 0000 (PST copy 0)
NOTE: group 1 PST updated.
Mon Sep 12 11:44:59 2016
NOTE: membership refresh pending for group 1/0x43c8b183 (DATADG)
Mon Sep 12 11:45:02 2016
NOTE: successfully read ACD block gn=1 blk=0 via retry read
Errors in file /u01/app/grid/diag/asm/+asm/+ASM1/trace/+ASM1_lgwr_3526.trc:
ORA-15062: ASM disk is globally closed
GMON querying group 1 at 13 for pid 18, osid 3532
NOTE: cache closing disk 1 of grp 1: (not open) _DROPPED_0001_DATADG
SUCCESS: refreshed membership for 1/0x43c8b183 (DATADG)
SUCCESS: alter diskgroup DATADG drop disk DATADG_0001 force /* ASM SERVER */
NOTE: starting rebalance of group 1/0x43c8b183 (DATADG) at power 1
SUCCESS: PST-initiated drop disk in group 1(1137226115))
Starting background process ARB0
Mon Sep 12 11:45:03 2016
ARB0 started with pid=35, OS id=19945
NOTE: assigning ARB0 to group 1/0x43c8b183 (DATADG) with 1 parallel I/O
cellip.ora not found.
NOTE: Rebalance has restored redundancy for any existing control file or redo log in disk group DATADG
NOTE: Attempting voting file refresh on diskgroup DATADG
NOTE: Refresh completed on diskgroup DATADG. No voting file found.
Mon Sep 12 11:46:21 2016
NOTE: GroupBlock outside rolling migration privileged region
NOTE: requesting all-instance membership refresh for group=1
Mon Sep 12 11:46:24 2016
GMON updating for reconfiguration, group 1 at 14 for pid 36, osid 20110
NOTE: cache closing disk 1 of grp 1: (not open) _DROPPED_0001_DATADG
NOTE: group 1 PST updated.
WARNING: offline disk number 1 has references (54679 AUs)
Mon Sep 12 11:46:24 2016
NOTE: membership refresh pending for group 1/0x43c8b183 (DATADG)
GMON querying group 1 at 15 for pid 18, osid 3532
NOTE: cache closing disk 1 of grp 1: (not open) _DROPPED_0001_DATADG
SUCCESS: refreshed membership for 1/0x43c8b183 (DATADG)
NOTE: Attempting voting file refresh on diskgroup DATADG
NOTE: Refresh completed on diskgroup DATADG. No voting file found.
NOTE: stopping process ARB0
SUCCESS: rebalance completed for group 1/0x43c8b183 (DATADG)

这里我们可以看出来磁盘组在2016年9月12日由于disk 1 无法响应，直接被asm 踢出了磁盘组

把被强制删除的磁盘重新加回去

Mon Mar 06 15:36:54 2017
SQL> alter diskgroup DATADG add disk '/dev/asm-diskdata01' name DATADG_0000
NOTE: GroupBlock outside rolling migration privileged region
ORA-15032: not all alterations performed
ORA-15029: disk '/dev/asm-diskdata01' is already mounted by this instance
ERROR: alter diskgroup DATADG add disk '/dev/asm-diskdata01' name DATADG_0000
Mon Mar 06 15:38:27 2017
SQL>  alter diskgroup DATADG add disk '/dev/asm-diskdata02' name DATADG_0001
NOTE: GroupBlock outside rolling migration privileged region
NOTE: Assigning number (1,2) to disk (/dev/asm-diskdata02)
NOTE: requesting all-instance membership refresh for group=1
NOTE: Disk DATADG_0001 in mode 0x7f marked for de-assignment
ERROR: ORA-15033 signalled during reconfiguration of diskgroup DATADG
Mon Mar 06 15:38:28 2017
NOTE: membership refresh pending for group 1/0x31584f6b (DATADG)
Mon Mar 06 15:38:31 2017
GMON querying group 1 at 7 for pid 18, osid 3468
NOTE: cache closing disk 1 of grp 1: (not open) _DROPPED_0001_DATADG
GMON querying group 1 at 8 for pid 18, osid 3468
NOTE: cache closing disk 1 of grp 1: (not open) _DROPPED_0001_DATADG
SUCCESS: refreshed membership for 1/0x31584f6b (DATADG)
ORA-15032: not all alterations performed
ORA-15033: disk '/dev/asm-diskdata02' belongs to diskgroup "DATADG"
ERROR:  alter diskgroup DATADG add disk '/dev/asm-diskdata02' name DATADG_0001
NOTE: Attempting voting file refresh on diskgroup DATADG
NOTE: Refresh completed on diskgroup DATADG. No voting file found.
Mon Mar 06 16:04:14 2017
SQL> alter diskgroup DATADG add disk '/dev/asm-diskdata02' name DATADG_0001
NOTE: GroupBlock outside rolling migration privileged region
NOTE: Assigning number (1,2) to disk (/dev/asm-diskdata02)
NOTE: requesting all-instance membership refresh for group=1
NOTE: Disk DATADG_0001 in mode 0x7f marked for de-assignment
ERROR: ORA-15033 signalled during reconfiguration of diskgroup DATADG
Mon Mar 06 16:04:15 2017
NOTE: membership refresh pending for group 1/0x31584f6b (DATADG)
Mon Mar 06 16:04:18 2017
GMON querying group 1 at 9 for pid 18, osid 3468
NOTE: cache closing disk 1 of grp 1: (not open) _DROPPED_0001_DATADG
GMON querying group 1 at 10 for pid 18, osid 3468
NOTE: cache closing disk 1 of grp 1: (not open) _DROPPED_0001_DATADG
SUCCESS: refreshed membership for 1/0x31584f6b (DATADG)
ORA-15032: not all alterations performed
ORA-15033: disk '/dev/asm-diskdata02' belongs to diskgroup "DATADG"
ERROR: alter diskgroup DATADG add disk '/dev/asm-diskdata02' name DATADG_0001
NOTE: Attempting voting file refresh on diskgroup DATADG
NOTE: Refresh completed on diskgroup DATADG. No voting file found.
Mon Mar 06 16:23:28 2017
SQL> alter diskgroup DATADG add FAILGROUP DATA_0001 disk '/dev/adm-diskdata02' name DATA_0001
NOTE: GroupBlock outside rolling migration privileged region
ORA-15032: not all alterations performed
ORA-15031: disk specification '/dev/adm-diskdata02' matches no disks
ERROR: alter diskgroup DATADG add FAILGROUP DATA_0001 disk '/dev/adm-diskdata02' name DATA_0001
Mon Mar 06 16:24:48 2017
SQL> alter diskgroup DATADG add FAILGROUP DATA_0001 disk '/dev/asm-diskdata02' name DATA_0001
NOTE: GroupBlock outside rolling migration privileged region
NOTE: Assigning number (1,2) to disk (/dev/asm-diskdata02)
NOTE: requesting all-instance membership refresh for group=1
NOTE: Disk DATA_0001 in mode 0x7f marked for de-assignment
ERROR: ORA-15033 signalled during reconfiguration of diskgroup DATADG
Mon Mar 06 16:24:49 2017
NOTE: membership refresh pending for group 1/0x31584f6b (DATADG)
Mon Mar 06 16:24:52 2017
GMON querying group 1 at 11 for pid 18, osid 3468
NOTE: cache closing disk 1 of grp 1: (not open) _DROPPED_0001_DATADG
GMON querying group 1 at 12 for pid 18, osid 3468
NOTE: cache closing disk 1 of grp 1: (not open) _DROPPED_0001_DATADG
SUCCESS: refreshed membership for 1/0x31584f6b (DATADG)
ORA-15032: not all alterations performed
ORA-15033: disk '/dev/asm-diskdata02' belongs to diskgroup "DATADG"
ERROR: alter diskgroup DATADG add FAILGROUP DATA_0001 disk '/dev/asm-diskdata02' name DATA_0001
NOTE: Attempting voting file refresh on diskgroup DATADG
NOTE: Refresh completed on diskgroup DATADG. No voting file found.
Mon Mar 06 16:26:07 2017
SQL> alter diskgroup DATADG add FAILGROUP DATA_0001 disk '/dev/asm-diskdata02' name DATA_0001 force
NOTE: GroupBlock outside rolling migration privileged region
NOTE: Assigning number (1,2) to disk (/dev/asm-diskdata02)
NOTE: requesting all-instance membership refresh for group=1
NOTE: initializing header on grp 1 disk DATA_0001
NOTE: requesting all-instance disk validation for group=1
Mon Mar 06 16:26:10 2017
NOTE: skipping rediscovery for group 1/0x31584f6b (DATADG) on local instance.
NOTE: requesting all-instance disk validation for group=1
NOTE: skipping rediscovery for group 1/0x31584f6b (DATADG) on local instance.
Mon Mar 06 16:26:15 2017
GMON updating for reconfiguration, group 1 at 13 for pid 28, osid 12861
NOTE: group 1 PST updated.
NOTE: initiating PST update: grp = 1
GMON updating group 1 at 14 for pid 28, osid 12861
NOTE: cache closing disk 1 of grp 1: (not open) _DROPPED_0001_DATADG
NOTE: group DATADG: updated PST location: disk 0000 (PST copy 0)
NOTE: group DATADG: updated PST location: disk 0002 (PST copy 1)
NOTE: PST update grp = 1 completed successfully
NOTE: membership refresh pending for group 1/0x31584f6b (DATADG)
GMON querying group 1 at 15 for pid 18, osid 3468
NOTE: cache closing disk 1 of grp 1: (not open) _DROPPED_0001_DATADG
NOTE: cache opening disk 2 of grp 1: DATA_0001 path:/dev/asm-diskdata02
NOTE: Attempting voting file refresh on diskgroup DATADG
NOTE: Refresh completed on diskgroup DATADG. No voting file found.
GMON querying group 1 at 16 for pid 18, osid 3468
NOTE: cache closing disk 1 of grp 1: (not open) _DROPPED_0001_DATADG
SUCCESS: refreshed membership for 1/0x31584f6b (DATADG)
Mon Mar 06 16:26:19 2017
SUCCESS: alter diskgroup DATADG add FAILGROUP DATA_0001 disk '/dev/asm-diskdata02' name DATA_0001 force
NOTE: starting rebalance of group 1/0x31584f6b (DATADG) at power 1
Mon Mar 06 16:26:20 2017
Starting background process ARB0
Mon Mar 06 16:26:20 2017
ARB0 started with pid=32, OS id=25833
NOTE: assigning ARB0 to group 1/0x31584f6b (DATADG) with 1 parallel I/O
cellip.ora not found.
WARNING:cache read  a corrupt block: group=1(DATADG) dsk=0 blk=0 disk=0
        (DATADG_0000)incarn=3915956130 au=0 blk=0 count=1
Errors in file /u01/app/grid/diag/asm/+asm/+ASM1/trace/+ASM1_arb0_25833.trc:
ORA-15196: invalid ASM block header [kfc.c:26368] [endian_kfbh] [2147483648] [0] [0 != 1]
NOTE:a corrupted block from group DATADG was dumped to /u01/app/grid/diag/asm/+asm/+ASM1/trace/+ASM1_arb0_25833.trc
WARNING:cache read (retry)a corrupt block:group=1(DATADG)
         dsk=0 blk=0 disk=0(DATADG_0000)incarn=3915956130 au=0 blk=0 count=1
Errors in file /u01/app/grid/diag/asm/+asm/+ASM1/trace/+ASM1_arb0_25833.trc:
ORA-15196: invalid ASM block header [kfc.c:26368] [endian_kfbh] [2147483648] [0] [0 != 1]
ORA-15196: invalid ASM block header [kfc.c:26368] [endian_kfbh] [2147483648] [0] [0 != 1]
ERROR: cache failed to read group=1(DATADG) dsk=0 blk=0 from disk(s): 0(DATADG_0000)
ORA-15196: invalid ASM block header [kfc.c:26368] [endian_kfbh] [2147483648] [0] [0 != 1]
ORA-15196: invalid ASM block header [kfc.c:26368] [endian_kfbh] [2147483648] [0] [0 != 1]
NOTE: cache initiating offline of disk 0 group DATADG
NOTE:process _arb0_+asm1 (25833) initiating offline of disk 0.3915956130(DATADG_0000)with mask 0x7e in group 1
NOTE: checking PST: grp = 1
GMON checking disk modes for group 1 at 17 for pid 32, osid 25833
NOTE: cache closing disk 1 of grp 1: (not open) _DROPPED_0001_DATADG
ERROR: too many offline disks in PST (grp 1)
NOTE: checking PST for grp 1 done.
NOTE: initiating PST update: grp = 1, dsk = 0/0xe968bfa2, mask = 0x6a, op = clear
GMON updating disk modes for group 1 at 18 for pid 32, osid 25833
NOTE: cache closing disk 1 of grp 1: (not open) _DROPPED_0001_DATADG
ERROR: Disk 0 cannot be offlined, since all the disks [0, 1] with mirrored data would be offline.
ERROR: too many offline disks in PST (grp 1)
Mon Mar 06 16:26:23 2017
NOTE: cache dismounting (not clean) group 1/0x31584F6B (DATADG)
NOTE: messaging CKPT to quiesce pins Unix process pid: 25889, image: oracle@DBN01 (B000)
Mon Mar 06 16:26:23 2017
NOTE: halting all I/Os to diskgroup 1 (DATADG)
Mon Mar 06 16:26:23 2017
NOTE: LGWR doing non-clean dismount of group 1 (DATADG)
NOTE: LGWR sync ABA=19.2851 last written ABA 19.2851
WARNING: Offline for disk DATADG_0000 in mode 0x7f failed.
Mon Mar 06 16:26:23 2017
kjbdomdet send to inst 2
detach from dom 1, sending detach message to inst 2
Mon Mar 06 16:26:23 2017
List of instances:
 1 2
Dirty detach reconfiguration started (new ddet inc 1, cluster inc 8)
Errors in file /u01/app/grid/diag/asm/+asm/+ASM1/trace/+ASM1_arb0_25833.trc  (incident=65537):
ORA-15335: ASM metadata corruption detected in disk group 'DATADG'
ORA-15130: diskgroup "DATADG" is being dismounted
ORA-15066: offlining disk "DATADG_0000" in group "DATADG" may result in a data loss
ORA-15196: invalid ASM block header [kfc.c:26368] [endian_kfbh] [2147483648] [0] [0 != 1]
ORA-15196: invalid ASM block header [kfc.c:26368] [endian_kfbh] [2147483648] [0] [0 != 1]
Incident details in:/u01/app/grid/diag/asm/+asm/+ASM1/incident/incdir_65537/+ASM1_arb0_25833_i65537.trc
 Global Resource Directory partially frozen for dirty detach
* dirty detach - domain 1 invalid = TRUE
 3189 GCS resources traversed, 0 cancelled
Dirty Detach Reconfiguration complete
ERROR: ORA-15130 in COD recovery for diskgroup 1/0x31584f6b (DATADG)
ERROR: ORA-15130 thrown in RBAL for group number 1
Errors in file /u01/app/grid/diag/asm/+asm/+ASM1/trace/+ASM1_rbal_3468.trc:
ORA-15130: diskgroup "DATADG" is being dismounted
Mon Mar 06 16:26:23 2017
WARNING: dirty detached from domain 1
NOTE: cache dismounted group 1/0x31584F6B (DATADG)
---后续mount报错
SQL> ALTER DISKGROUP DATADG MOUNT  /* asm agent *//* {1:18003:2} */
NOTE: cache registered group DATADG number=1 incarn=0xb368408f
NOTE: cache began mount (first) of group DATADG number=1 incarn=0xb368408f
NOTE: Assigning number (1,2) to disk (/dev/asm-diskdata02)
WARNING:GMON has insufficient disks to maintain consensus.
Minimum required is 2:updating 1 PST copies from a total of 2.
ERROR: GMON failed to obtain a quorum ofsupporting disks in group 1
NOTE: cache dismounting (clean) group 1/0xB368408F (DATADG)
NOTE: messaging CKPT to quiesce pins Unix process pid: 27651, image: oracle@DBN01 (TNS V1-V3)
NOTE: dbwr not being msg'd to dismount
NOTE: lgwr not being msg'd to dismount
NOTE: cache dismounted group 1/0xB368408F (DATADG)
NOTE: cache ending mount (fail) of group DATADG number=1 incarn=0xb368408f
NOTE: cache deleting context for group DATADG 1/0xb368408f
GMON dismounting group 1 at 12 for pid 30, osid 27651
NOTE: Disk DATA_0001 in mode 0x9 marked for de-assignment
ERROR: diskgroup DATADG was not mounted
ORA-15032: not all alterations performed
ORA-15017: diskgroup "DATADG" cannot be mounted
ORA-15315: Write errors in disk group DATADG could lead to inconsistent ASM metadata.
ERROR: ALTER DISKGROUP DATADG MOUNT  /* asm agent *//* {1:18003:2} */

从这里我们可以看出来，前几次加asm disk 由于各种原因都失败了，最后一次通过加force关键字，使得被自动drop的disk重新强制加到datadg里面.可悲的是在加入成功之后,开始做rebalance的时候，发现disk 0出现坏块,从而引起ORA-15196的错误，使得rebalance无法进行下去,进而整个asm 磁盘组datadg自动dismount.后面再次尝试mount datadg的时候，直接提示元数据库不一致，因为disk 0 的磁盘头已经异常.

通过kfed分析disk 0信息
这里是通过dd命令备份的磁盘头到win进行分析的,以前正常的disk 0的磁盘头损坏(全0)

对于这个故障已经比较清楚，恢复思路也基本上确定：依次递进
方案1：通过kfed修改文件头，然后尝试mount磁盘头手工修复ASM DISK HEADER 异常
方案2：直接通过amdu,dul之类的工具拷贝出来数据文件找回ASM中数据文件
方案3：通过底层au重组出来数据文件asm disk header 彻底损坏恢复
在我们的实际恢复中运气比较好，通过方案1就完成了恢复工作，通过kfed修复磁盘头之后，然后报错如下

SQL> alter diskgroup DATADG mount
NOTE: cache registered group DATADG number=1 incarn=0x5134d0d4
NOTE: cache began mount (first) of group DATADG number=1 incarn=0x5134d0d4
NOTE: Assigning number (1,2) to disk (/dev/asm-diskdata02)
NOTE: Assigning number (1,0) to disk (/dev/asm-diskdata01)
Tue Mar 07 19:03:40 2017
NOTE: GMON heartbeating for grp 1
GMON querying group 1 at 27 for pid 28, osid 13837
NOTE: Assigning number (1,1) to disk ()
GMON querying group 1 at 28 for pid 28, osid 13837
NOTE: cache closing disk 1 of grp 1: (not open)
NOTE: cache opening disk 0 of grp 1: DATADG_0000 path:/dev/asm-diskdata01
NOTE: F1X0 found on disk 0 au 2 fcn 0.178802
NOTE: cache opening disk 2 of grp 1: DATA_0001 path:/dev/asm-diskdata02
NOTE: cache mounting (first) normal redundancy group 1/0x5134D0D4 (DATADG)
Tue Mar 07 19:03:40 2017
* allocate domain 1, invalid = TRUE
kjbdomatt send to inst 2
Tue Mar 07 19:03:40 2017
NOTE: attached to recovery domain 1
NOTE: starting recovery of thread=1 ckpt=19.2851 group=1 (DATADG)
NOTE: starting recovery of thread=2 ckpt=13.5327 group=1 (DATADG)
NOTE: advancing ckpt for group 1 (DATADG) thread=2 ckpt=13.5327
NOTE: advancing ckpt for group 1 (DATADG) thread=1 ckpt=19.2852
NOTE: cache recovered group 1 to fcn 0.365868
NOTE: redo buffer size is 512 blocks (2101760 bytes)
Tue Mar 07 19:03:40 2017
NOTE: LGWR attempting to mount thread 1 for diskgroup 1 (DATADG)
NOTE: LGWR found thread 1 closed at ABA 19.2851
NOTE: LGWR mounted thread 1 for diskgroup 1 (DATADG)
NOTE: LGWR opening thread 1 at fcn 0.365868 ABA 20.2852
NOTE: cache mounting group 1/0x5134D0D4 (DATADG) succeeded
NOTE: cache ending mount (success) of group DATADG number=1 incarn=0x5134d0d4
Tue Mar 07 19:03:40 2017
NOTE: Instance updated compatible.asm to 11.2.0.0.0 for grp 1
SUCCESS: diskgroup DATADG was mounted
SUCCESS: alter diskgroup DATADG mount
Tue Mar 07 19:03:40 2017
NOTE: diskgroup resource ora.DATADG.dg is online
Tue Mar 07 19:03:41 2017
ASM Health Checker found 1 new failures
NOTE: ASM did background COD recovery for group 1/0x5134d0d4 (DATADG)
NOTE: starting rebalance of group 1/0x5134d0d4 (DATADG) at power 1
Starting background process ARB0
Tue Mar 07 19:03:42 2017
ARB0 started with pid=30, OS id=13905
NOTE: assigning ARB0 to group 1/0x5134d0d4 (DATADG) with 1 parallel I/O
cellip.ora not found.
WARNING: cache read  a corrupt block: group=1(DATADG) dsk=0 blk=0 disk=0
         (DATADG_0000) incarn=2202280062 au=0 blk=0 count=1
Errors in file /u01/app/grid/diag/asm/+asm/+ASM1/trace/+ASM1_arb0_13905.trc:
ORA-15196: invalid ASM block header [kfc.c:26368] [blk_kfbl] [2147483648] [0] [1022 != 0]
NOTE: a corrupted block from group DATADG was dumped to /u01/app/grid/diag/asm/+asm/+ASM1/trace/+ASM1_arb0_13905.trc
WARNING:cache read (retry)a corrupt block:group=1(DATADG) dsk=0 blk=0 disk=0
        (DATADG_0000)incarn=2202280062 au=0 blk=0 count=1
Errors in file /u01/app/grid/diag/asm/+asm/+ASM1/trace/+ASM1_arb0_13905.trc:
ORA-15196: invalid ASM block header [kfc.c:26368] [blk_kfbl] [2147483648] [0] [1022 != 0]
ORA-15196: invalid ASM block header [kfc.c:26368] [blk_kfbl] [2147483648] [0] [1022 != 0]
ERROR: cache failed to read group=1(DATADG) dsk=0 blk=0 from disk(s): 0(DATADG_0000)
ORA-15196: invalid ASM block header [kfc.c:26368] [blk_kfbl] [2147483648] [0] [1022 != 0]
ORA-15196: invalid ASM block header [kfc.c:26368] [blk_kfbl] [2147483648] [0] [1022 != 0]
Tue Mar 07 19:03:52 2017
NOTE: client oradb1:oradb registered, osid 13989, mbr 0x1
NOTE: cache initiating offline of disk 0 group DATADG
NOTE:process _arb0_+asm1 (13905) initiating offline of disk 0.2202280062(DATADG_0000)with mask 0x7e in group 1
NOTE: checking PST: grp = 1
Tue Mar 07 19:03:52 2017
GMON checking disk modes for group 1 at 30 for pid 30, osid 13905
NOTE: cache closing disk 1 of grp 1: (not open) _DROPPED_0001_DATADG
ERROR: too many offline disks in PST (grp 1)
NOTE: checking PST for grp 1 done.
NOTE: initiating PST update: grp = 1, dsk = 0/0x8344207e, mask = 0x6a, op = clear
GMON updating disk modes for group 1 at 31 for pid 30, osid 13905
NOTE: cache closing disk 1 of grp 1: (not open) _DROPPED_0001_DATADG
ERROR: Disk 0 cannot be offlined, since all the disks [0, 1] with mirrored data would be offline.
ERROR: too many offline disks in PST (grp 1)
Tue Mar 07 19:03:52 2017
NOTE: cache dismounting (not clean) group 1/0x5134D0D4 (DATADG)
WARNING: Offline for disk DATADG_0000 in mode 0x7f failed.
Tue Mar 07 19:03:52 2017
NOTE: halting all I/Os to diskgroup 1 (DATADG)
NOTE: messaging CKPT to quiesce pins Unix process pid: 14002, image: oracle@DBN01 (B000)
Errors in file /u01/app/grid/diag/asm/+asm/+ASM1/trace/+ASM1_arb0_13905.trc  (incident=76402):
ORA-15335: ASM metadata corruption detected in disk group 'DATADG'
ORA-15130: diskgroup "DATADG" is being dismounted
ORA-15066: offlining disk "DATADG_0000" in group "DATADG" may result in a data loss
ORA-15196: invalid ASM block header [kfc.c:26368] [blk_kfbl] [2147483648] [0] [1022 != 0]
ORA-15196: invalid ASM block header [kfc.c:26368] [blk_kfbl] [2147483648] [0] [1022 != 0]
Incident details in: /u01/app/grid/diag/asm/+asm/+ASM1/incident/incdir_76402/+ASM1_arb0_13905_i76402.trc
Tue Mar 07 19:03:52 2017
NOTE: LGWR doing non-clean dismount of group 1 (DATADG)
NOTE: LGWR sync ABA=20.2857 last written ABA 20.2857

这里比较比较幸运，datadg已经mount成功了，但是由于rab依旧读取到disk header异常信息(没有完全修复成功,而且在日志中不光这个block异常，还有其他block异常，因此不考虑进一步修复),因此直接通过屏蔽asm的acd和cod实现该磁盘组mount,而且不会dismount。

SQL> alter diskgroup DATADG mount
NOTE: cache registered group DATADG number=1 incarn=0x9c94d0eb
NOTE: cache began mount (first) of group DATADG number=1 incarn=0x9c94d0eb
NOTE: Assigning number (1,2) to disk (/dev/asm-diskdata02)
NOTE: Assigning number (1,0) to disk (/dev/asm-diskdata01)
NOTE: skip COD recovery as part of test at kfrc.c:1639
NOTE: skip COD recovery as part of test at kfrc.c:1639
Tue Mar 07 19:12:45 2017
NOTE: GMON heartbeating for grp 1
GMON querying group 1 at 75 for pid 28, osid 15615
NOTE: Assigning number (1,1) to disk ()
GMON querying group 1 at 76 for pid 28, osid 15615
NOTE: cache closing disk 1 of grp 1: (not open)
NOTE: cache opening disk 0 of grp 1: DATADG_0000 path:/dev/asm-diskdata01
NOTE: F1X0 found on disk 0 au 2 fcn 0.178802
NOTE: cache opening disk 2 of grp 1: DATA_0001 path:/dev/asm-diskdata02
NOTE: cache mounting (first) normal redundancy group 1/0x9C94D0EB (DATADG)
Tue Mar 07 19:12:45 2017
* allocate domain 1, invalid = TRUE
kjbdomatt send to inst 2
Tue Mar 07 19:12:45 2017
NOTE: attached to recovery domain 1
NOTE: starting recovery of thread=1 ckpt=25.2870 group=1 (DATADG)
NOTE: advancing ckpt for group 1 (DATADG) thread=1 ckpt=25.2873
NOTE: cache recovered group 1 to fcn 0.365897
NOTE: redo buffer size is 512 blocks (2101760 bytes)
Tue Mar 07 19:12:45 2017
NOTE: LGWR attempting to mount thread 1 for diskgroup 1 (DATADG)
NOTE: LGWR found thread 1 closed at ABA 25.2872
NOTE: LGWR mounted thread 1 for diskgroup 1 (DATADG)
NOTE: LGWR opening thread 1 at fcn 0.365897 ABA 26.2873
NOTE: cache mounting group 1/0x9C94D0EB (DATADG) succeeded
NOTE: cache ending mount (success) of group DATADG number=1 incarn=0x9c94d0eb
Tue Mar 07 19:12:45 2017
NOTE: Instance updated compatible.asm to 11.2.0.0.0 for grp 1
SUCCESS: diskgroup DATADG was mounted
SUCCESS: alter diskgroup DATADG mount
Tue Mar 07 19:12:45 2017
NOTE: diskgroup resource ora.DATADG.dg is online
NOTE: skip COD recovery as part of test at kfrc.c:1639
NOTE: skip COD recovery as part of test at kfrc.c:1639
NOTE: skip COD recovery as part of test at kfrc.c:1639
NOTE: skip COD recovery as part of test at kfrc.c:1639

asm的问题解决后，然后登录数据库，发现运气比较好，两个数据库正常open成功，而且alert日志无任何报错，直接通过rman备份出来数据，重建asm磁盘组，还原数据，恢复完成，而且实现数据0丢失。
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