在asm 磁盘组不能mount的情况下,如果是磁盘头的少数部分损坏,或者是asm disk header存在,可以通过kfed修复,或者使用备份的磁盘头信息去恢复从而实现磁盘组mount来恢复数据库.如果没有备份也无法修复可以尝试使用amdu,dul来实现对不能mount的磁盘组进行恢复.

在asm 磁盘组不能mount的情况下,如果是磁盘头的少数部分损坏,或者是asm disk header存在,可以通过kfed修复,或者使用备份的磁盘头信息去恢复从而实现磁盘组mount来恢复数据库.如果没有备份也无法修复可以尝试使用amdu,dul来实现对不能mount的磁盘组进行恢复.在极端情况下(比如磁盘组完全丢失),amdu/dul都无论为力的情况下,可以考虑使用扫描磁盘找出来datafile 的方法求救数据的最后稻草.本实验大概的模拟了asm disk 前10M完全损坏的情况下数据库恢复
测试准备
创建新表空间，创建T_XIFENFEI测试表

SQL> create tablespace xifenfei datafile '+XIFENFEI' SIZE 50m;
Tablespace created.
SQL> CREATE TABLE T_XIFENFEI TABLESPACE XIFENFEI
 2 AS SELECT * FROM DBA_OBJECTS;
Table created.
SQL> SELECT COUNT(*) FROM T_XIFENFEI;
 COUNT(*)
----------
 50031
SQL> select ts#,rfile#,bytes/1024/1024,blocks,name from v$datafile;
 TS# RFILE# BYTES/1024/1024 BLOCKS NAME
---------- ---------- --------------- ---------- --------------------------------------------------
 0 1 480 61440 +XIFENFEI/asm10g/datafile/system.256.845260203
 1 2 25 3200 +XIFENFEI/asm10g/datafile/undotbs1.258.845260205
 2 3 250 32000 +XIFENFEI/asm10g/datafile/sysaux.257.845260203
 4 4 5 0 +XIFENFEI/asm10g/datafile/users.259.845260205
 6 5 50 00 +XIFENFEI/asm10g/datafile/xifenfei.266.845262139
SQL> select GROUP_NUMBER,DISK_NUMBER,STATE,TOTAL_MB,FREE_MB,NAME,path from v$asm_disk;
GROUP_NUMBER DISK_NUMBER STATE TOTAL_MB FREE_MB NAME PATH
------------ ----------- -------- ---------- ---------- -------------------- ------------------
 1 0 NORMAL 2048 0 XIFENFEI_0000 /dev/raw/raw1
 1 1 NORMAL 784 0 XIFENFEI_0001 /dev/raw/raw2
 1 2 NORMAL 7059 0 XIFENFEI_0002 /dev/raw/raw3
--关闭数据库
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
--关闭ASM
SQL> shutdown immediate
ASM diskgroups dismounted
ASM instance shutdown

查看裸设备对应磁盘

[oracle@xifenfei dul]$ more /etc/sysconfig/rawdevices
/dev/raw/raw1 /dev/sdc
/dev/raw/raw2 /dev/sdd1
/dev/raw/raw3 /dev/sdd2

dd磁盘头
dd asm disk 前面10M，彻底破坏asm disk

[oracle@xifenfei ~]$ dd if=/dev/zero of=/dev/raw/raw1 bs=1M count=10 conv=notrunc 
10+0 records in
10+0 records out
10485760 bytes (10 MB) copied, 0.175424 seconds, 59.8 MB/s
[oracle@xifenfei ~]$ dd if=/dev/zero of=/dev/raw/raw2 bs=1M count=10 conv=notrunc 
10+0 records in
10+0 records out
10485760 bytes (10 MB) copied, 0.11584 seconds, 90.5 MB/s
[oracle@xifenfei ~]$ dd if=/dev/zero of=/dev/raw/raw3 bs=1M count=10 conv=notrunc 
10+0 records in
10+0 records out
10485760 bytes (10 MB) copied, 0.353435 seconds, 29.7 MB/s

kfed查看磁盘
确定所有asm disk header完全被破坏

[oracle@xifenfei dul]$ kfed read /dev/raw/raw1
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
[oracle@xifenfei dul]$ kfed read /dev/raw/raw2
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
[oracle@xifenfei dul]$ kfed read /dev/raw/raw3
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

amdu查看asm 磁盘

[oracle@xifenfei ~]$ amdu -diskstring '/dev/raw/raw*'
amdu_2014_04_18_23_17_17/
[oracle@xifenfei ~]$ cd amdu_2014_04_18_23_17_17
[oracle@xifenfei amdu_2014_04_18_23_17_17]$ ls
report.txt
[oracle@xifenfei amdu_2014_04_18_23_17_17]$ more report.txt 
-*-amdu-*-
…………
--------------------------------- Operations ---------------------------------
------------------------------- Disk Selection -------------------------------
 -diskstring '/dev/raw/raw*'
------------------------------ Reading Control -------------------------------
------------------------------- Output Control -------------------------------
********************************* DISCOVERY **********************************
----------------------------- DISK REPORT N0001 ------------------------------
 Disk Path: /dev/raw/raw1
 Unique Disk ID: 
 Disk Label: 
 Physical Sector Size: 512 bytes
 Disk Size: 65536 megabytes
** NOT A VALID ASM DISK HEADER. BAD VALUE IN FIELD blksize_kfdhdb **
----------------------------- DISK REPORT N0002 ------------------------------
 Disk Path: /dev/raw/raw2
 Unique Disk ID: 
 Disk Label: 
 Physical Sector Size: 512 bytes
 Disk Size: 65536 megabytes
** NOT A VALID ASM DISK HEADER. BAD VALUE IN FIELD blksize_kfdhdb **
----------------------------- DISK REPORT N0003 ------------------------------
 Disk Path: /dev/raw/raw3
 Unique Disk ID: 
 Disk Label: 
 Physical Sector Size: 512 bytes
 Disk Size: 65536 megabytes
** NOT A VALID ASM DISK HEADER. BAD VALUE IN FIELD blksize_kfdhdb **
******************************* END OF REPORT ********************************

通过这里证明，当asm disk header 损坏严重之时,amdu无法识别，更加无法恢复相关数据库

dul查看完全损坏asm disk header
测试在asm disk header完全损坏情况下,dul是否还能够实现asm磁盘组中抽取数据,同理amdu也无法正常工作.

[oracle@xifenfei dul]$ ./dul
Data UnLoader: 10.2.0.5.28 - Internal Only - on Sat Apr 19 04:02:02 2014
with -bit io functions
Copyright (c) 1994 2014 Bernard van Duijnen All rights reserved.
 Strictly Oracle Internal Use Only
DUL: Warning: block 0 is not a disk header block
DUL: Error: Block is not in use
DUL: Error: Block type mismatch ( seen 0 expect 1) when parsing block 0 of disk /dev/raw/raw1
DUL: Warning: block 0 is not a disk header block
DUL: Error: Block is not in use
DUL: Error: Block type mismatch ( seen 0 expect 1) when parsing block 0 of disk /dev/raw/raw2
DUL: Warning: block 0 is not a disk header block
DUL: Error: Block is not in use
DUL: Error: Block type mismatch ( seen 0 expect 1) when parsing block 0 of disk /dev/raw/raw3

这里可以看出来,当asm disk header完全异常,dul也无法识别出来asm磁盘组(该情况下dul无法正常操作)

通过工具扫描磁盘抽取数据块

CPFL> scan disk /dev/raw/raw1
Scanning disk /dev/raw/raw1, at 2014-04-19 04:05:11
Completed disk /dev/raw/raw1, at 2014-04-19 04:05:56
CPFL> scan disk /dev/raw/raw1
Scanning disk /dev/raw/raw1, at 2014-04-19 04:05:56
Completed disk /dev/raw/raw1, at 2014-04-19 04:06:15
CPFL> scan disk /dev/raw/raw1
Scanning disk /dev/raw/raw1, at 2014-04-19 04:06:15
Completed disk /dev/raw/raw1, at 2014-04-19 04:07:44
CPFL> list datafiles
 Tablespace: SYSTEM File: 1 Blocks: 61440 
 Tablespace: UNDOTBS1 File: 2 Blocks: 3200 
 Tablespace: SYSAUX File: 3 Blocks: 32000 
 Tablespace: USERS File: 4 Blocks: 0 
 Tablespace: XIFENFEI File: 5 Blocks: 00 
CPFL> copy datafile 1 to /u01/oracle/oradata/datafile/1.dbf
copy datafile start: 2014-04-19 04:10:35
copy datafile 1 have blocks 61440
copy datafile completed: 2014-04-19 04:11:18
CPFL> copy datafile 2 to /u01/oracle/oradata/datafile/2.dbf
copy datafile start: 2014-04-19 04:11:52
copy datafile 2 have blocks 3200
copy datafile completed: 2014-04-19 04:11:54
CPFL> copy datafile 3 to /u01/oracle/oradata/datafile/3.dbf
copy datafile start: 2014-04-19 04:12:03
copy datafile 3 have blocks 32000
copy datafile completed: 2014-04-19 04:12:27
CPFL> copy datafile 4 to /u01/oracle/oradata/datafile/4.dbf
copy datafile start: 2014-04-19 04:13:07
copy datafile 4 have blocks 0
copy datafile completed: 2014-04-19 04:13:08
CPFL> copy datafile 5 to /u01/oracle/oradata/datafile/5.dbf
copy datafile start: 2014-04-19 04:13:18
copy datafile 5 have blocks 00
copy datafile completed: 2014-04-19 04:13:19

查看使用工具抽取数据文件

[oracle@xifenfei datafile]$ ls -l
total 830320
-rw-r--r-- 1 oracle oinstall 503324672 Apr 19 04:34 1.dbf
-rw-r--r-- 1 oracle oinstall 26222592 Apr 19 04:34 2.dbf
-rw-r--r-- 1 oracle oinstall 262152192 Apr 19 04:34 3.dbf
-rw-r--r-- 1 oracle oinstall 5251072 Apr 19 04:34 4.dbf
-rw-r--r-- 1 oracle oinstall 52436992 Apr 19 04:34 5.dbf

dul验证抽取文件

[oracle@xifenfei dul]$ ./dul
Data UnLoader: 10.2.0.5.28 - Internal Only - on Sat Apr 19 06:56:09 2014
with -bit io functions
Copyright (c) 1994 2014 Bernard van Duijnen All rights reserved.
 Strictly Oracle Internal Use Only
DUL: Warning: Recreating file "dul.log"
Found db_id = 181793355
Found db_name = ASM10G
DUL> show datafiles;
ts# rf# start blocks offs open err file name
 0 1 0 61440 0 1 0 /u01/oracle/oradata/datafile/1.dbf
 1 2 0 3200 0 1 0 /u01/oracle/oradata/datafile/2.dbf
 2 3 0 32000 0 1 0 /u01/oracle/oradata/datafile/3.dbf
 4 4 0 0 0 1 0 /u01/oracle/oradata/datafile/4.dbf
 6 5 0 00 0 1 0 /u01/oracle/oradata/datafile/5.dbf
DUL> bootstrap;
Probing file = 1, block = 377
. unloading table BOOTSTRAP$
DUL: Warning: block number is non zero but marked deferred trying to process it anyhow
 57 rows unloaded
DUL: Warning: Dictionary cache DC_BOOTSTRAP is empty
Reading BOOTSTRAP.dat 57 entries loaded
Parsing Bootstrap$ contents
DUL: Warning: Recreating file "dict.ddl"
Generating dict.ddl for version 10
 OBJ$: segobjno 18, file 1 block 121
 TAB$: segobjno 2, tabno 1, file 1 block 25
 COL$: segobjno 2, tabno 5, file 1 block 25
 USER$: segobjno 10, tabno 1, file 1 block 
Running generated file "@dict.ddl" to unload the dictionary tables
. unloading table OBJ$ 51171 rows unloaded
. unloading table TAB$ 1576 rows unloaded
. unloading table COL$ 552 rows unloaded
. unloading table USER$ 59 rows unloaded
Reading USER.dat 59 entries loaded
Reading OBJ.dat 51171 entries loaded and sorted 51171 entries
Reading TAB.dat 1576 entries loaded
Reading COL.dat 552 entries loaded and sorted 552 entries
Reading BOOTSTRAP.dat 57 entries loaded
DUL: Warning: Recreating file "dict.ddl"
Generating dict.ddl for version 10
 OBJ$: segobjno 18, file 1 block 121
 TAB$: segobjno 2, tabno 1, file 1 block 25
 COL$: segobjno 2, tabno 5, file 1 block 25
 USER$: segobjno 10, tabno 1, file 1 block 
 TABPART$: segobjno 266, file 1 block 2121
 INDPART$: segobjno 271, file 1 block 2161
 TABCOMPART$: segobjno 288, file 1 block 2297
 INDCOMPART$: segobjno 293, file 1 block 2345
 TABSUBPART$: segobjno 278, file 1 block 2217
 INDSUBPART$: segobjno 283, file 1 block 2257
 IND$: segobjno 2, tabno 3, file 1 block 25
 ICOL$: segobjno 2, tabno 4, file 1 block 25
 LOB$: segobjno 2, tabno 6, file 1 block 25
 COLTYPE$: segobjno 2, tabno 7, file 1 block 25
 TYPE$: segobjno 181, tabno 1, file 1 block 1297
 COLLECTION$: segobjno 181, tabno 2, file 1 block 1297
 ATTRIBUTE$: segobjno 181, tabno 3, file 1 block 1297
 LOBFRAG$: segobjno 299, file 1 block 2393
 LOBCOMPPART$: segobjno 302, file 1 block 2425
 UNDO$: segobjno 15, file 1 block 105
 TS$: segobjno 6, tabno 2, file 1 block 57
 PROPS$: segobjno 96, file 1 block 721
Running generated file "@dict.ddl" to unload the dictionary tables
. unloading table OBJ$
DUL: Warning: Recreating file "OBJ.ctl"
 51171 rows unloaded
. unloading table TAB$
DUL: Warning: Recreating file "TAB.ctl"
 1576 rows unloaded
. unloading table COL$
DUL: Warning: Recreating file "COL.ctl"
 552 rows unloaded
. unloading table USER$
DUL: Warning: Recreating file "USER.ctl"
 59 rows unloaded
. unloading table TABPART$ 72 rows unloaded
. unloading table INDPART$ 80 rows unloaded
. unloading table TABCOMPART$ 0 rows unloaded
. unloading table INDCOMPART$ 0 rows unloaded
. unloading table TABSUBPART$ 0 rows unloaded
. unloading table INDSUBPART$ 0 rows unloaded
. unloading table IND$ 2231 rows unloaded
. unloading table ICOL$ 3650 rows unloaded
. unloading table LOB$ 530 rows unloaded
. unloading table COLTYPE$ 1701 rows unloaded
. unloading table TYPE$ 1945 rows unloaded
. unloading table COLLECTION$ 555 rows unloaded
. unloading table ATTRIBUTE$ 7275 rows unloaded
. unloading table LOBFRAG$ 1 row unloaded
. unloading table LOBCOMPPART$ 0 rows unloaded
. unloading table UNDO$ 21 rows unloaded
. unloading table TS$ 7 rows unloaded
. unloading table PROPS$ 28 rows unloaded
Reading USER.dat 59 entries loaded
Reading OBJ.dat 51171 entries loaded and sorted 51171 entries
Reading TAB.dat 1576 entries loaded
Reading COL.dat 552 entries loaded and sorted 552 entries
Reading TABPART.dat 72 entries loaded and sorted 72 entries
Reading TABCOMPART.dat 0 entries loaded and sorted 0 entries
Reading TABSUBPART.dat 0 entries loaded and sorted 0 entries
Reading INDPART.dat 80 entries loaded and sorted 80 entries
Reading INDCOMPART.dat 0 entries loaded and sorted 0 entries
Reading INDSUBPART.dat 0 entries loaded and sorted 0 entries
Reading IND.dat 2231 entries loaded
Reading LOB.dat 530 entries loaded
Reading ICOL.dat 3650 entries loaded
Reading COLTYPE.dat 1701 entries loaded
Reading TYPE.dat 1945 entries loaded
Reading ATTRIBUTE.dat 7275 entries loaded
Reading COLLECTION.dat 555 entries loaded
Reading BOOTSTRAP.dat 57 entries loaded
Reading LOBFRAG.dat 1 entries loaded and sorted 1 entries
Reading LOBCOMPPART.dat 0 entries loaded and sorted 0 entries
Reading UNDO.dat 21 entries loaded
Reading TS.dat 7 entries loaded
Reading PROPS.dat 28 entries loaded
Database character set is ZHS16GBK
Database national character set is AL16UTF16
DUL> unload table sys.t_xifenfei;
. unloading table T_XIFENFEI 50031 rows unloaded

通过这里可以发现,我们创建测试数据为50031条,dul读取抽取出来数据文件中对应表数据条数也为50031条;证明:在asm disk header完全损坏情况下,amdu,dul无法直接恢复asm里面数据库，但是可以通过工具扫描数据文件，找出来磁盘中的datafile block实现完整恢复数据[只要你的asm中的数据没有覆盖,都可以通过该方法恢复]

如果你在使用这些思路进行恢复遇到突发情况不能自行解决,请联系我们(ORACLE数据库恢复技术支持),将为您提供专业数据库技术支持：
Phone:134298788 Q Q:1074445 E-Mail:dba@xifenfei.com

原文地址：asm disk header 彻底损坏恢复, 感谢原作者分享。