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标题：分享oracleasm createdisk重新创建asm disk后数据0丢失恢复案例
作者：惜分飞©版权所有[未经本人同意,不得以任何形式转载,否则有进一步追究法律责任的权利.]
有客户反馈他们重启系统之后，发现asmlib创建的asmdisk丢失了，然后又使用oracleasm deletedisk和createdisk重新创建的asm disk，最后发现asm diskgroup无法mount。让客户通过dd 备份5m数据，然后使用kfed分析
kefd分析结果
E:\OneDrive\ORACLE\recover\no_backup\asm\kfedwin>kfed read H:\temp\asmlib\xx.img kfbh.endian: 0 ; 0x000: 0x00 kfbh.hard: 0 ; 0x001: 0x00 kfbh.type: 0 ; 0x002: KFBTYP_INVALID kfbh.datfmt: 0 ; 0x003: 0x00 kfbh.block.blk: 0 ; 0x004: T=0 NUMB=0x0 kfbh.block.obj: 0 ; 0x008: TYPE=0x0 NUMB=0x0 kfbh.check: 3760689243 ; 0x00c: 0xe027905b kfbh.fcn.base: 0 ; 0x010: 0x00000000 kfbh.fcn.wrap: 0 ; 0x014: 0x00000000 kfbh.spare1: 0 ; 0x018: 0x00000000 kfbh.spare2: 0 ; 0x01c: 0x00000000 E:\OneDrive\ORACLE\recover\no_backup\asm\kfedwin>kfed read H:\temp\asmlib\xx.img blkn=1 kfbh.endian: 0 ; 0x000: 0x00 kfbh.hard: 0 ; 0x001: 0x00 kfbh.type: 0 ; 0x002: KFBTYP_INVALID kfbh.datfmt: 0 ; 0x003: 0x00 kfbh.block.blk: 0 ; 0x004: T=0 NUMB=0x0 kfbh.block.obj: 0 ; 0x008: TYPE=0x0 NUMB=0x0 kfbh.check: 0 ; 0x00c: 0x00000000 kfbh.fcn.base: 0 ; 0x010: 0x00000000 kfbh.fcn.wrap: 0 ; 0x014: 0x00000000 kfbh.spare1: 0 ; 0x018: 0x00000000 kfbh.spare2: 0 ; 0x01c: 0x00000000 E:\OneDrive\ORACLE\recover\no_backup\asm\kfedwin>kfed read H:\temp\asmlib\xx.img blkn=10 kfbh.endian: 0 ; 0x000: 0x00 kfbh.hard: 0 ; 0x001: 0x00 kfbh.type: 0 ; 0x002: KFBTYP_INVALID kfbh.datfmt: 0 ; 0x003: 0x00 kfbh.block.blk: 0 ; 0x004: T=0 NUMB=0x0 kfbh.block.obj: 0 ; 0x008: TYPE=0x0 NUMB=0x0 kfbh.check: 0 ; 0x00c: 0x00000000 kfbh.fcn.base: 0 ; 0x010: 0x00000000 kfbh.fcn.wrap: 0 ; 0x014: 0x00000000 kfbh.spare1: 0 ; 0x018: 0x00000000 kfbh.spare2: 0 ; 0x01c: 0x00000000 E:\OneDrive\ORACLE\recover\no_backup\asm\kfedwin>kfed read H:\temp\asmlib\xx.img blkn=255 kfbh.endian: 0 ; 0x000: 0x00 kfbh.hard: 0 ; 0x001: 0x00 kfbh.type: 0 ; 0x002: KFBTYP_INVALID kfbh.datfmt: 0 ; 0x003: 0x00 kfbh.block.blk: 0 ; 0x004: T=0 NUMB=0x0 kfbh.block.obj: 0 ; 0x008: TYPE=0x0 NUMB=0x0 kfbh.check: 0 ; 0x00c: 0x00000000 kfbh.fcn.base: 0 ; 0x010: 0x00000000 kfbh.fcn.wrap: 0 ; 0x014: 0x00000000 kfbh.spare1: 0 ; 0x018: 0x00000000 kfbh.spare2: 0 ; 0x01c: 0x00000000 E:\OneDrive\ORACLE\recover\no_backup\asm\kfedwin>kfed read H:\temp\asmlib\xx.img blkn=256|more kfbh.endian: 1 ; 0x000: 0x01 kfbh.hard: 130 ; 0x001: 0x82 kfbh.type: 17 ; 0x002: KFBTYP_PST_META kfbh.datfmt: 2 ; 0x003: 0x02 kfbh.block.blk: 256 ; 0x004: T=0 NUMB=0x100 kfbh.block.obj: 2147483648 ; 0x008: TYPE=0x8 NUMB=0x0 kfbh.check: 3925268785 ; 0x00c: 0xe9f6d931 kfbh.fcn.base: 0 ; 0x010: 0x00000000 kfbh.fcn.wrap: 0 ; 0x014: 0x00000000 kfbh.spare1: 0 ; 0x018: 0x00000000 kfbh.spare2: 0 ; 0x01c: 0x00000000 kfdpHdrPairBv1.first.super.time.hi:32994098 ; 0x000: HOUR=0x12 DAYS=0x19 MNTH=0x c YEAR=0x7dd kfdpHdrPairBv1.first.super.time.lo:1614030848 ; 0x004: USEC=0x0 MSEC=0x10a SECS= 0x3 MINS=0x18 kfdpHdrPairBv1.first.super.last: 2 ; 0x008: 0x00000002 kfdpHdrPairBv1.first.super.next: 2 ; 0x00c: 0x00000002 kfdpHdrPairBv1.first.super.copyCnt: 1 ; 0x010: 0x01 kfdpHdrPairBv1.first.super.version: 1 ; 0x011: 0x01 kfdpHdrPairBv1.first.super.ub2spare: 0 ; 0x012: 0x0000 kfdpHdrPairBv1.first.super.incarn: 1 ; 0x014: 0x00000001 kfdpHdrPairBv1.first.super.copy[0]: 0 ; 0x018: 0x0000 kfdpHdrPairBv1.first.super.copy[1]: 0 ; 0x01a: 0x0000 kfdpHdrPairBv1.first.super.copy[2]: 0 ; 0x01c: 0x0000 ……
因为kfed默认每个block为4k，这里提示256是ok的，255是损坏的，从而推测出来，很可能oracleasm createdisk损坏了1M的数据。由于默认au是1m，而且数据库版本是11.2.0.3，而且第256个blkn开始没有损坏，因此初步判断可以考虑使用备份asm disk header来恢复磁盘头
检查还原磁盘头的asm disk
[grid@xifenfei1 disks]$ kfed read DATA1 kfbh.endian: 1 ; 0x000: 0x01 kfbh.hard: 130 ; 0x001: 0x82 kfbh.type: 1 ; 0x002: KFBTYP_DISKHEAD kfbh.datfmt: 1 ; 0x003: 0x01 kfbh.block.blk: 0 ; 0x004: blk=0 kfbh.block.obj: 2147483648 ; 0x008: disk=0 kfbh.check: 2776451033 ; 0x00c: 0xa57d47d9 kfbh.fcn.base: 0 ; 0x010: 0x00000000 kfbh.fcn.wrap: 0 ; 0x014: 0x00000000 kfbh.spare1: 0 ; 0x018: 0x00000000 kfbh.spare2: 0 ; 0x01c: 0x00000000 kfdhdb.driver.provstr: ORCLDISKDATA1 ; 0x000: length=13 kfdhdb.driver.reserved[0]: 1096040772 ; 0x008: 0x41544144 kfdhdb.driver.reserved[1]: 49 ; 0x00c: 0x00000031 kfdhdb.driver.reserved[2]: 0 ; 0x010: 0x00000000 kfdhdb.driver.reserved[3]: 0 ; 0x014: 0x00000000 kfdhdb.driver.reserved[4]: 0 ; 0x018: 0x00000000 kfdhdb.driver.reserved[5]: 0 ; 0x01c: 0x00000000 kfdhdb.compat: 186646528 ; 0x020: 0x0b200000 kfdhdb.dsknum: 0 ; 0x024: 0x0000 kfdhdb.grptyp: 1 ; 0x026: KFDGTP_EXTERNAL kfdhdb.hdrsts: 3 ; 0x027: KFDHDR_MEMBER kfdhdb.dskname: DATA_0000 ; 0x028: length=9 kfdhdb.grpname: DATA ; 0x048: length=4 kfdhdb.fgname: DATA_0000 ; 0x068: length=9 kfdhdb.capname: ; 0x088: length=0 kfdhdb.crestmp.hi: 32994099 ; 0x0a8: HOUR=0x13 DAYS=0x19 MNTH=0xc YEAR=0x7dd kfdhdb.crestmp.lo: 2797442048 ; 0x0ac: USEC=0x0 MSEC=0x365 SECS=0x2b MINS=0x29 kfdhdb.mntstmp.hi: 33022061 ; 0x0b0: HOUR=0xd DAYS=0x3 MNTH=0x8 YEAR=0x7df kfdhdb.mntstmp.lo: 816879616 ; 0x0b4: USEC=0x0 MSEC=0x26 SECS=0xb MINS=0xc kfdhdb.secsize: 512 ; 0x0b8: 0x0200 kfdhdb.blksize: 4096 ; 0x0ba: 0x1000 …………
证明磁盘头确实被比较完美的修复了，现在的任务是尝试mount磁盘组
mount磁盘组
[grid@xifenfei1 ~]$ sqlplus / as sysasm SQL*Plus: Release 11.2.0.3.0 Production on Thu Aug 6 20:54:53 2015 Copyright (c) 1982, 2011, Oracle. All rights reserved. Connected to: Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production With the Real Application Clusters and Automatic Storage Management options SQL> alter diskgroup data mount; Diskgroup altered. SQL> exit Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production With the Real Application Clusters and Automatic Storage Management options
asm diskgroup已经正常mount，使用asmcmd命令检查文件是否正常
分析磁盘组数据是否正常
[grid@xifenfei1 ~]$ asmcmd ASMCMD> lsdg State Type Rebal Sector Block AU Total_MB Free_MB Req_mir_free_MB Usable_file_MB Offline_disks Voting_files Name MOUNTED EXTERN N 512 4096 1048576 1622060 636493 0 636493 0 N DATA/ ASMCMD> cd data ASMCMD> ls ORCL/ ASMCMD> cd orcl ASMCMD> ls CONTROLFILE/ DATAFILE/ ONLINELOG/ PARAMETERFILE/ TEMPFILE/ spfileorcl.ora ASMCMD> cd datafile ASMCMD> ls XIFENFEI20130801.314.835191517 XIFENFEI20140101.321.835191571 XIFENFEI20140201.322.835191573 XIFENFEI20140301.323.835191573 ………… SYSAUX.270.835182535 SYSAUX.838.874669369 SYSTEM.271.835182533 SYSTEM.823.873555791 SYSTEM.945.883146947 …………
这里看到磁盘组里面的数据文件都正常，使用同样的方法，继续mount其他磁盘组。
尝试启动数据库
SQL> startup ORACLE 例程已经启动。 Total System Global Area 5010685952 bytes Fixed Size 2236968 bytes Variable Size 2013269464 bytes Database Buffers 2986344448 bytes Redo Buffers 8835072 bytes 数据库装载完毕。 ORA-16038: 日志 14 sequence# 21145 无法归档 ORA-19504: 无法创建文件"" ORA-00312: 联机日志 14 线程 2: '+DATA/orcl/onlinelog/group_14.284.835184569' ORA-00312: 联机日志 14 线程 2: '+ARCH/orcl/onlinelog/group_14.287.835184569'
查看数据库alert日志
ARC1: Archival started ARC2: Archival started ARC2: Becoming the 'no FAL' ARCH ARC2: Becoming the 'no SRL' ARCH ARC1: Becoming the heartbeat ARCH ARC3: Archival started ARC0: STARTING ARCH PROCESSES COMPLETE Thu Aug 06 21:04:06 2015 Thread 2 advanced to log sequence 21146 (thread recovery) Picked broadcast on commit scheme to generate SCNs Thread 2 advanced to log sequence 21147 (before internal thread enable) Errors in file /u01/app/oracle/diag/rdbms/orcl/orcl1/trace/orcl1_ora_27402.trc: ORA-19816: 警告: 文件可能存在于数据库未知的 db_recovery_file_dest 中。 ORA-17502: ksfdcre: 4 未能创建文件 +ARCH ORA-15196: invalid ASM block header [kfc.c:19572] [check_kfbh] [1] [47962] [1344818371 != 630731762] ORA-15130: diskgroup "ARCH" is being dismounted ORA-15066: offlining disk "ARCH_0000" in group "ARCH" may result in a data loss ORA-15196: invalid ASM block header [kfc.c:26076] [endian_kfbh] [2147483648] [1] [0 != 1] ORA-15196: invalid ASM block header [kfc.c:26076] [endian_kfbh] [2147483648] [1] [0 != 1] ARCH: Error 19504 Creating archive log file to '+ARCH' NOTE: Deferred communication with ASM instance Errors in file /u01/app/oracle/diag/rdbms/orcl/orcl1/trace/orcl1_ora_27402.trc: ORA-15130: diskgroup "ARCH" is being dismounted NOTE: deferred map free for map id 754 Errors in file /u01/app/oracle/diag/rdbms/orcl/orcl1/trace/orcl1_ora_27402.trc: ORA-16038: 日志 14 sequence# 21145 无法归档 ORA-19504: 无法创建文件"" ORA-00312: 联机日志 14 线程 2: '+DATA/orcl/onlinelog/group_14.284.835184569' ORA-00312: 联机日志 14 线程 2: '+ARCH/orcl/onlinelog/group_14.287.835184569' ORA-16038 signalled during: ALTER DATABASE OPEN... Thu Aug 06 21:04:10 2015 SUCCESS: diskgroup ARCH was dismounted SUCCESS: diskgroup ARCH was dismounted Thu Aug 06 21:04:10 2015 Errors in file /u01/app/oracle/diag/rdbms/orcl/orcl1/trace/orcl1_ckpt_27353.trc: ORA-00206: error in writing (block 3, # blocks 1) of control file ORA-00202: control file: '+ARCH/orcl/controlfile/current.256.835182531' ORA-15078: ASM diskgroup was forcibly dismounted ORA-15078: ASM diskgroup was forcibly dismounted Errors in file /u01/app/oracle/diag/rdbms/orcl/orcl1/trace/orcl1_ckpt_27353.trc: ORA-00221: error on write to control file ORA-00206: error in writing (block 3, # blocks 1) of control file ORA-00202: control file: '+ARCH/orcl/controlfile/current.256.835182531' ORA-15078: ASM diskgroup was forcibly dismounted ORA-15078: ASM diskgroup was forcibly dismounted Thu Aug 06 21:04:10 2015 System state dump requested by (instance=1, osid=27353 (CKPT)), summary=[abnormal instance termination]. System State dumped to trace file /u01/app/oracle/diag/rdbms/orcl/orcl1/trace/orcl1_diag_27318.trc CKPT (ospid: 27353): terminating the instance due to error 221 Instance terminated by CKPT, pid = 27353
查看asm alert日志
Thu Aug 06 21:04:07 2015 WARNING: cache read a corrupt block: group=2(ARCH) dsk=0 blk=1 disk=0 (ARCH_0000) incarn=3942486752 au=0 blk=1 count=1 Errors in file /u01/app/11.2.0/grid/log/diag/asm/+asm/+ASM1/trace/+ASM1_ora_27462.trc: ORA-15196: invalid ASM block header [kfc.c:26076] [endian_kfbh] [2147483648] [1] [0 != 1] NOTE: a corrupted block from group ARCH was dumped to /u01/app/11.2.0/grid/log/diag/asm/+asm/+ASM1/trace/+ASM1_ora_27462.trc WARNING: cache read (retry) a corrupt block: group=2(ARCH) dsk=0 blk=1 disk=0 (ARCH_0000) incarn=3942486752 au=0 blk=1 count=1 Errors in file /u01/app/11.2.0/grid/log/diag/asm/+asm/+ASM1/trace/+ASM1_ora_27462.trc: ORA-15196: invalid ASM block header [kfc.c:26076] [endian_kfbh] [2147483648] [1] [0 != 1] ORA-15196: invalid ASM block header [kfc.c:26076] [endian_kfbh] [2147483648] [1] [0 != 1] ERROR: cache failed to read group=2(ARCH) dsk=0 blk=1 from disk(s): 0(ARCH_0000) ORA-15196: invalid ASM block header [kfc.c:26076] [endian_kfbh] [2147483648] [1] [0 != 1] ORA-15196: invalid ASM block header [kfc.c:26076] [endian_kfbh] [2147483648] [1] [0 != 1] NOTE: cache initiating offline of disk 0 group ARCH NOTE: process _user27462_+asm1 (27462) initiating offline of disk 0.3942486752 (ARCH_0000) with mask 0x7e in group 2 WARNING: Disk 0 (ARCH_0000) in group 2 in mode 0x7f is now being taken offline on ASM inst 1 NOTE: initiating PST update: grp = 2, dsk = 0/0xeafd92e0, mask = 0x6a, op = clear Thu Aug 06 21:04:07 2015 GMON updating disk modes for group 2 at 17 for pid 35, osid 27462 ERROR: Disk 0 cannot be offlined, since diskgroup has external redundancy. ERROR: too many offline disks in PST (grp 2) Thu Aug 06 21:04:07 2015 NOTE: cache dismounting (not clean) group 2/0x723D6245 (ARCH) NOTE: messaging CKPT to quiesce pins Unix process pid: 27089, image: oracle@xifenfei1 (B000) WARNING: Offline of disk 0 (ARCH_0000) in group 2 and mode 0x7f failed on ASM inst 1 Thu Aug 06 21:04:07 2015 NOTE: halting all I/Os to diskgroup 2 (ARCH) System State dumped to trace file /u01/app/11.2.0/grid/log/diag/asm/+asm/+ASM1/trace/+ASM1_ora_27462.trc NOTE: AMDU dump of disk group ARCH created at /u01/app/11.2.0/grid/log/diag/asm/+asm/+ASM1/trace Thu Aug 06 21:04:09 2015 NOTE: LGWR doing non-clean dismount of group 2 (ARCH) NOTE: LGWR sync ABA=126.806 last written ABA 126.806
这里可以看出来,报错的block为arch磁盘组的第一个磁盘的第一个au的第二个block，而我们在开始的时候，已经分析了asm disk的第一个au完全损坏，并且我们使用了备份磁盘头进行来还原，勉强可以让磁盘组mount起来，但是由于数据库在启动的时候，需要对redo进行归档，而归档的过程需要写到arch磁盘组里面，这个时候需要访问到au=0 blk=1,而这个块本身是坏的，因此这个时候该块盘的disk就被offline掉了，而这个磁盘组是外部冗余的，因此磁盘组dismount了，所以数据库无法启动.
分析第一个au里面到底有哪些东西
SQL> select DISK_NUMBER,path from v$asm_disk;
DISK_NUMBER PATH
----------- --------------------------------------------------
0 /dev/raw/raw1
2 /dev/raw/raw3
1 /dev/raw/raw2
[oracle@xifenfei raw]$ kfed read raw1 blkn=1|grep kfbh.type
kfbh.type: 2 ; 0x002: KFBTYP_FREESPC
[oracle@xifenfei raw]$ kfed read raw1 blkn=2|grep kfbh.type
kfbh.type: 3 ; 0x002: KFBTYP_ALLOCTBL
[oracle@xifenfei raw]$ kfed read raw1 blkn=3|grep kfbh.type
kfbh.type: 3 ; 0x002: KFBTYP_ALLOCTBL
[oracle@xifenfei raw]$ kfed read raw1 blkn=255|grep kfbh.type
kfbh.type: 3 ; 0x002: KFBTYP_ALLOCTBL
[oracle@xifenfei raw]$ kfed read raw2 blkn=1|grep kfbh.type
kfbh.type: 2 ; 0x002: KFBTYP_FREESPC
[oracle@xifenfei raw]$ kfed read raw2 blkn=2|grep kfbh.type
kfbh.type: 3 ; 0x002: KFBTYP_ALLOCTBL
[oracle@xifenfei raw]$ kfed read raw2 blkn=255|grep kfbh.type
kfbh.type: 3 ; 0x002: KFBTYP_ALLOCTBL
[oracle@xifenfei raw]$ kfed read raw3 blkn=1|grep kfbh.type
kfbh.type: 2 ; 0x002: KFBTYP_FREESPC
[oracle@xifenfei raw]$ kfed read raw3 blkn=2|grep kfbh.type
kfbh.type: 3 ; 0x002: KFBTYP_ALLOCTBL
[oracle@xifenfei raw]$ kfed read raw3 blkn=255|grep kfbh.type
kfbh.type: 3 ; 0x002: KFBTYP_ALLOCTBL
通过一个测试机器的一个磁盘组进行分析，我们可以基本上确定asm 第一个au除了asm disk header的KFBTYP_DISKHEAD之外，其他主要是KFBTYP_FREESPC(Free Space Table)和KFBTYP_ALLOCTBL(allocator table)，主要就是记录asm中au的分配情况，也就是进一步说明，如果我不对asm里面的数据使用更多的au分配或者回收au，在缺少第一个au的1-255个block的信息情况下，asm的磁盘组也不会dismount。根据这个思路，让数据库归档到本地，然后继续测试
继续open数据库
SQL> startup ORACLE 例程已经启动。 Total System Global Area 5010685952 bytes Fixed Size 2236968 bytes Variable Size 2013269464 bytes Database Buffers 2986344448 bytes Redo Buffers 8835072 bytes 数据库装载完毕。 SQL> alter database open; 数据库已更改。 LGWR: STARTING ARCH PROCESSES COMPLETE ARC0: STARTING ARCH PROCESSES Fri Aug 07 02:43:13 2015 ARC1 started with pid=34, OS id=22778 Fri Aug 07 02:43:13 2015 ARC2 started with pid=35, OS id=22780 Fri Aug 07 02:43:13 2015 ARC3 started with pid=36, OS id=22782 ARC1: Archival started ARC2: Archival started ARC2: Becoming the 'no FAL' ARCH ARC2: Becoming the 'no SRL' ARCH ARC1: Becoming the heartbeat ARCH ARC3: Archival started ARC0: STARTING ARCH PROCESSES COMPLETE Fri Aug 07 02:43:24 2015 Thread 1 opened at log sequence 18604 Current log# 10 seq# 18604 mem# 0: /tmp/xifenfei/otherfile/group_10.273.835182533 Current log# 10 seq# 18604 mem# 1: /tmp/xifenfei/otherfile/group_10.263.835182533 Successful open of redo thread 1 Fri Aug 07 02:43:24 2015 MTTR advisory is disabled because FAST_START_MTTR_TARGET is not set Fri Aug 07 02:43:25 2015 SMON: enabling cache recovery Instance recovery: looking for dead threads Instance recovery: lock domain invalid but no dead threads Fri Aug 07 02:43:26 2015 minact-scn: Inst 1 is now the master inc#:2 mmon proc-id:21328 status:0x7 minact-scn status: grec-scn:0x0000.00000000 gmin-scn:0x0000.00000000 gcalc-scn:0x0000.00000000 Fri Aug 07 02:43:26 2015 Redo thread 2 internally disabled at seq 21147 (CKPT) [21341] Successfully onlined Undo Tablespace 2. Undo initialization finished serial:0 start:96999124 end:97000624 diff:1500 (15 seconds) Verifying file header compatibility for 11g tablespace encryption.. Verifying 11g file header compatibility for tablespace encryption completed SMON: enabling tx recovery Database Characterset is ZHS16GBK No Resource Manager plan active Starting background process GTX0 Fri Aug 07 02:43:31 2015 GTX0 started with pid=37, OS id=22803 Starting background process RCBG Fri Aug 07 02:43:31 2015 RCBG started with pid=38, OS id=22805 replication_dependency_tracking turned off (no async multimaster replication found) Fri Aug 07 02:43:34 2015 Archived Log entry 73876 added for thread 2 sequence 21145 ID 0x513c613f dest 1: <---果然有归档操作发生 Starting background process QMNC Fri Aug 07 02:43:34 2015 QMNC started with pid=39, OS id=22812 Fri Aug 07 02:43:35 2015 Archived Log entry 73877 added for thread 2 sequence 21146 ID 0x513c613f dest 1: Fri Aug 07 02:43:35 2015 ARC0: Archiving disabled thread 2 sequence 21147 Archived Log entry 73878 added for thread 2 sequence 21147 ID 0x513c613f dest 1: Fri Aug 07 02:43:37 2015 Completed: alter database open
现在到了这一步，基本上可以确定，数据库是零丢失恢复。由于asm 第一个au丢失数据严重，想要彻底修复比较难，考虑把数据库启动到mount/read only状态然后使用rman备份数据，然后进行重建asm 磁盘组，再迁移回来。至此完美恢复asmlib的磁盘被oracleasm重写的故障恢复，实现数据0丢失.当然在整个恢复过程没有于此的简单,涉及到在votedisk损坏的情况下,如何mount磁盘组，vote diskgroup的损坏修复问题,磁盘组在10g/11.1和11.2还原磁盘头备份的问题等问题.
虽然本次的恢复案例中，由于asmlib的asm disk不可见就轻易使用oracleasm createdisk命令对磁盘进行了重建，犯了一个很大错误，但是在重建之后，发现磁盘组依旧异常，未继续操作(比如重建磁盘组等)，为最后的数据完全恢复创造了必要条件，使得客户的没有任何数据损失。如果再对除磁盘组继续复写操作，可能会导致数据永久性丢失。这个教训告诉我们：遇到自己不能把握的事情，及时终止，不要让错误越走越远
如果asmdisk 真的重建成功了 而且在没有备份的情况下 岂不是连数据都没了。真敢做啊。。。
如果是再次创建了磁盘组，那就是diskgroup的磁盘组字典大量损坏，不能使用这种方法恢复，可以通过工具直接扫描磁盘恢复数据文件出来
惜分飞,
噢 明白了 通过工具直接读取asm磁盘组上，可以正常读出来的数据，可以恢复到其他环境下，最大限度的确保数据的不丢失，当然还是取决于asm为损坏的部分工具能读出来部分。 我去研究研究kfed。。。
有些情况下，损坏的asm 字典比较多，kfed也无能为力，需要一些磁盘重组的工具来谁，抢救数据