在有些情况下,我们仅有一份rman备份,而这个时候rman 备份有出现坏块,使得我们的还原/恢复工作无法继续下去,导致数据大量丢失.我们可以通过设置event 19548/19549来跳过坏块,最大程度抢救数据
rman备份数据文件

C:\Users\XIFENFEI>rman target /

Recovery Manager: Release 11.2.0.3.0 - Production on Thu Jun 6 20:31:19 2013

Copyright (c) 1982, 2011, Oracle and/or its affiliates.  All rights reserved.

connected to target database: XIFENFEI (DBID=1422012639)

RMAN> backup tablespace users format 'f:/users_bak.rman';

Starting backup at 06-JUN-13
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=197 device type=DISK
channel ORA_DISK_1: starting full datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
input datafile file number=00004 name=E:\ORACLE\ORADATA\XIFENFEI\USERS01.DBF
channel ORA_DISK_1: starting piece 1 at 06-JUN-13
channel ORA_DISK_1: finished piece 1 at 06-JUN-13
piece handle=F:\USERS_BAK.RMAN tag=TAG20130606T203154 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:03
Finished backup at 06-JUN-13

切换归档日志

SQL> alter system switch logfile;

System altered.

SQL> /

System altered.

SQL> /

System altered.

SQL> archive log list;
Database log mode              Archive Mode
Automatic archival             Enabled
Archive destination            E:\oracle\product\11.2.0\dbhome_1\RDBMS
Oldest online log sequence     95
Next log sequence to archive   97
Current log sequence           97

重命名数据文件

SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.

--------------------------------------
e:\oracle\oradata\XIFENFEI>move USERS01.DBF USERS01_bak.DBF
移动了         1 个文件。
--------------------------------------

SQL> startup
ORACLE instance started.

Total System Global Area  418484224 bytes
Fixed Size                  1385052 bytes
Variable Size             327159204 bytes
Database Buffers           83886080 bytes
Redo Buffers                6053888 bytes
Database mounted.
ORA-01157: cannot identify/lock data file 4 - see DBWR trace file
ORA-01110: data file 4: 'E:\ORACLE\ORADATA\XIFENFEI\USERS01.DBF'

破坏备份集
破坏前

破坏后

这里很明显,我通过ue把rman备份集中的T修改为了A,肯定破坏了文件,使之出现坏块

rman还原数据文件

C:\Users\XIFENFEI>rman target /

Recovery Manager: Release 11.2.0.3.0 - Production on Thu Jun 6 21:02:41 2013

Copyright (c) 1982, 2011, Oracle and/or its affiliates.  All rights reserved.

connected to target database: XIFENFEI (DBID=1422012639, not open)

RMAN> restore datafile 4;

Starting restore at 06-JUN-13
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=63 device type=DISK

channel ORA_DISK_1: starting datafile backup set restore
channel ORA_DISK_1: specifying datafile(s) to restore from backup set
channel ORA_DISK_1: restoring datafile 00004 to E:\ORACLE\ORADATA\XIFENFEI\USERS
01.DBF
channel ORA_DISK_1: reading from backup piece F:\USERS_BAK.RMAN
channel ORA_DISK_1: ORA-19870: error while restoring backup piece F:\USERS_BAK.R
MAN
ORA-19612: datafile 4 not restored due to missing or corrupt data

failover to previous backup

creating datafile file number=4 name=E:\ORACLE\ORADATA\XIFENFEI\USERS01.DBF
Finished restore at 06-JUN-13

这里可以清晰的看到rman报ORA-19612错误，restore 失败,alert日志为:

Thu Jun 06 21:02:31 2013
ALTER DATABASE OPEN
Errors in file E:\ORACLE\diag\rdbms\xifenfei\xff\trace\xff_dbw0_7400.trc:
ORA-01157: ????/?????? 4 - ??? DBWR ????
ORA-01110: ???? 4: 'E:\ORACLE\ORADATA\XIFENFEI\USERS01.DBF'
ORA-27041: ??????
OSD-04002: unable to open file
O/S-Error: (OS 2) 系统找不到指定的文件。
Errors in file E:\ORACLE\diag\rdbms\xifenfei\xff\trace\xff_ora_4272.trc:
ORA-01157: cannot identify/lock data file 4 - see DBWR trace file
ORA-01110: data file 4: 'E:\ORACLE\ORADATA\XIFENFEI\USERS01.DBF'
ORA-1157 signalled during: ALTER DATABASE OPEN...
Thu Jun 06 21:02:33 2013
Checker run found 1 new persistent data failures
Thu Jun 06 21:03:23 2013
Corrupt block 101 found during reading backup piece, file=F:\USERS_BAK.RMAN, corr_type=3
Reread of blocknum=101, file=F:\USERS_BAK.RMAN, found same corrupt data
Reread of blocknum=101, file=F:\USERS_BAK.RMAN, found same corrupt data
Reread of blocknum=101, file=F:\USERS_BAK.RMAN, found same corrupt data
Reread of blocknum=101, file=F:\USERS_BAK.RMAN, found same corrupt data
Reread of blocknum=101, file=F:\USERS_BAK.RMAN, found same corrupt data
Continuing reading piece F:\USERS_BAK.RMAN, no other copies available.

rman备份集有坏块，导致rman还原无法正常进行下去,还原后的数据文件大小

观察已经正常还原出来数据文件情况

SQL> select CHECKPOINT_CHANGE#,file# from v$datafile_header;

CHECKPOINT_CHANGE#      FILE#
------------------ ----------
           1571582          1
           1571582          2
           1571582          3
             18379          4
           1571582          5
           1571582          6
           1571582          7

SQL> recover database datafile 4 ;
ORA-00274: illegal recovery option DATAFILE


SQL> recover datafile 4;
ORA-00279: change 18379 generated at 01/20/2013 17:13:56 needed for thread 1
ORA-00289: suggestion :
E:\ORACLE\PRODUCT\11.2.0\DBHOME_1\RDBMS\ARC0000000001_0805223583.0001
ORA-00280: change 18379 for thread 1 is in sequence #1


Specify log: {<RET>=suggested | filename | AUTO | CANCEL}

rman只是还原了很小的一部分文件,做恢复提示需要从归档日志seq 1开始(某些情况可能需要其他归档,总之不是正常情况),证明rman还原异常

设置event事件还原

SQL> shutdown abort;
ORACLE instance shut down.
SQL> startup pfile='e:/pfile.txt' mount;
ORACLE instance started.

Total System Global Area  418484224 bytes
Fixed Size                  1385052 bytes
Variable Size             327159204 bytes
Database Buffers           83886080 bytes
Redo Buffers                6053888 bytes
Database mounted.
SQL> show parameter event;

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
event                                string      19548 trace name context forev
                                                 er, 19549 trace name context f
                                                 orever

Event 19548:This will attempt to restore content of the corrupted block if it is possible.
Event 19549:This will suppress erroring out during restore

rman还原数据文件

RMAN> restore datafile 4;

Starting restore at 06-JUN-13
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=63 device type=DISK

channel ORA_DISK_1: starting datafile backup set restore
channel ORA_DISK_1: specifying datafile(s) to restore from backup set
channel ORA_DISK_1: restoring datafile 00004 to E:\ORACLE\ORADATA\XIFENFEI\USERS
01.DBF
channel ORA_DISK_1: reading from backup piece F:\USERS_BAK.RMAN
channel ORA_DISK_1: piece handle=F:\USERS_BAK.RMAN tag=TAG20130606T203154
channel ORA_DISK_1: restored backup piece 1
channel ORA_DISK_1: restore complete, elapsed time: 00:00:35
Finished restore at 06-JUN-13

这里证明数据库rman有坏块通过rman还原成功,alert日志提示如下

Thu Jun 06 21:29:53 2013
WARNING: The block that appears to be block number 100
         in file 4 is corrupt in backup piece F:\USERS_BAK.RMAN.
         Such blocks would usually be formatted as empty
         in the restored file, but event 19548 has been
         set to include the block as-is in the restored
         file.
Corrupt block 102 found during reading backup piece, file=F:\USERS_BAK.RMAN, corr_type=-2
Reread of blocknum=102, file=F:\USERS_BAK.RMAN, found same corrupt data
Reread of blocknum=102, file=F:\USERS_BAK.RMAN, found same corrupt data
Reread of blocknum=102, file=F:\USERS_BAK.RMAN, found same corrupt data
Reread of blocknum=102, file=F:\USERS_BAK.RMAN, found same corrupt data
Reread of blocknum=102, file=F:\USERS_BAK.RMAN, found same corrupt data
Continuing reading piece F:\USERS_BAK.RMAN, no other copies available.
…………
Corrupt block 258 found during reading backup piece, file=F:\USERS_BAK.RMAN, corr_type=-2
Reread of blocknum=258, file=F:\USERS_BAK.RMAN, found same corrupt data
Reread of blocknum=258, file=F:\USERS_BAK.RMAN, found same corrupt data
Reread of blocknum=258, file=F:\USERS_BAK.RMAN, found same corrupt data
Reread of blocknum=258, file=F:\USERS_BAK.RMAN, found same corrupt data
Reread of blocknum=258, file=F:\USERS_BAK.RMAN, found same corrupt data
Continuing reading piece F:\USERS_BAK.RMAN, no other copies available.
WARNING: some data in the backup of file 4 was missing
         or corrupt.  Event 19549 has been set to allow
         the file to be restored anyway.
           backup header block count: 5369
           backup actual block count: 5212
              backup header checksum: -218250743
              backup actual checksum: 1442665538
Full restore complete of datafile 4 E:\ORACLE\ORADATA\XIFENFEI\USERS01.DBF.  Elapsed time: 0:00:25 
  checkpoint is 1570136
  last deallocation scn is 1508457

这里rman还原依然遇到很多坏块,但是均跳过坏块,还是完整的恢复出来的数据文件(大小)

rman还原数据文件

RMAN> recover datafile 4;

Starting recover at 06-JUN-13
using channel ORA_DISK_1

starting media recovery

archived log for thread 1 with sequence 94 is already on disk as file E:\ORACLE\
PRODUCT\11.2.0\DBHOME_1\RDBMS\ARC0000000094_0805223583.0001
archived log for thread 1 with sequence 95 is already on disk as file E:\ORACLE\
PRODUCT\11.2.0\DBHOME_1\RDBMS\ARC0000000095_0805223583.0001
archived log for thread 1 with sequence 96 is already on disk as file E:\ORACLE\
PRODUCT\11.2.0\DBHOME_1\RDBMS\ARC0000000096_0805223583.0001
archived log file name=E:\ORACLE\PRODUCT\11.2.0\DBHOME_1\RDBMS\ARC0000000094_080
5223583.0001 thread=1 sequence=94
media recovery complete, elapsed time: 00:00:00
Finished recover at 06-JUN-13

这里可以明显的看到在recover过程中数据库应用的是备份后的所有归档,数据文件是正常被还原出来(坏块除外)

查询对象

SQL> alter database open;

Database altered.

SQL> conn test/test
Connected.
SQL> select * from tab;

TNAME                          TABTYPE  CLUSTERID
------------------------------ ------- ----------
STB101                         TABLE

SQL> select count(*) from stb101;
select count(*) from stb101
                     *
ERROR at line 1:
ORA-08103: object no longer exists

dbv检查坏块

e:\oracle\oradata\XIFENFEI>dbv file=USERS01.DBF

DBVERIFY: Release 11.2.0.3.0 - Production on Thu Jun 6 23:59:49 2013

Copyright (c) 1982, 2011, Oracle and/or its affiliates.  All rights reserved.

DBVERIFY - Verification starting : FILE = E:\ORACLE\ORADATA\XIFENFEI\USERS01.DBF

Page 100 is marked corrupt
Corrupt block relative dba: 0x01000064 (file 4, block 100)
Bad check value found during dbv:
Data in bad block:
 type: 30 format: 2 rdba: 0x01000064
 last change scn: 0x0000.00004890 seq: 0x1 flg: 0x04
 spare1: 0x0 spare2: 0x0 spare3: 0x0
 consistency value in tail: 0x48901e01
 check value in block header: 0x8311
 computed block checksum: 0x20



DBVERIFY - Verification complete

Total Pages Examined         : 12320
Total Pages Processed (Data) : 4952
Total Pages Failing   (Data) : 0
Total Pages Processed (Index): 0
Total Pages Failing   (Index): 0
Total Pages Processed (Other): 7069
Total Pages Processed (Seg)  : 0
Total Pages Failing   (Seg)  : 0
Total Pages Empty            : 298

证明设置了event之后，rman确实跳过了备份集中的坏块,而且是直接还原了坏块内容,证明了event 19548和19549作用

补充说明
在非特殊情况下强烈不建议设置相关event跳过rman中的坏块来还原/恢复数据库,这样将对数据的丢失,甚至数据库是否可以正常open不好评估,rman备份重要,确保rman备份可用也很重要.