惜分飞

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