RMAN进行基于数据块的恢复
从ORACLE9i开始，rman支持基于数据库的恢复，这一功能有很大的好处，既不影响业务，甚至不影响有坏块的数据文件，恢复可以是在线恢复。但是恢复是完全恢复，所以要求完整的备份。
下面测试：
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对数据库进行完整备份
Rman>backup database;
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破坏数据
参看日志《RMAN进行基于数据块的恢复》
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使用rman验证数据文件
RMAN> backup validate datafile 5;
Starting backup at 29-AUG-14
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: sid=159 devtype=DISK
allocated channel: ORA_DISK_2
channel ORA_DISK_2: sid=139 devtype=DISK
channel ORA_DISK_1: starting full datafile backupset
channel ORA_DISK_1: specifying datafile(s) in backupset
input datafile fno=00005 name=/opt/oracle/oradata/orcla/xzsp.dbf
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:07
Finished backup at 29-AUG-14
警告日志和数据库中都会记录损坏的数据，如下
SQL> select * from v$database_block_corruption ;
FILE# BLOCK# BLOCKS CORRUPTION_CHANGE# CORRUPTIO
---------- ---------- ---------- ------------------ ---------
5 49316 1 0 CORRUPT
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通过备份基于数据快级的恢复
RMAN> blockrecover datafile 5 block 49316 from backupset;
Starting blockrecover at 29-AUG-14
using channel ORA_DISK_1
using channel ORA_DISK_2
channel ORA_DISK_1: restoring block(s)
channel ORA_DISK_1: specifying block(s) to restore from backup set
restoring blocks of datafile 00005
channel ORA_DISK_1: reading from backup piece /opt/oracle/flash_recovery_area1/ORCLA/backupset/2014_08_29/o1_mf_nnndf_TAG20140829T032828_9zz0px68_.bkp
channel ORA_DISK_1: restored block(s) from backup piece 1
piece handle=/opt/oracle/flash_recovery_area1/ORCLA/backupset/2014_08_29/o1_mf_nnndf_TAG20140829T032828_9zz0px68_.bkp tag=TAG20140829T032828
channel ORA_DISK_1: block restore complete, elapsed time: 00:00:26
starting media recovery
archive log thread 1 sequence 5 is already on disk as file /opt/oracle/flash_recovery_area1/ORCLA/archivelog/2014_08_29/o1_mf_1_5_9zz2mqwo_.arc
archive log thread 1 sequence 6 is already on disk as file /opt/oracle/flash_recovery_area1/ORCLA/archivelog/2014_08_29/o1_mf_1_6_9zz2v3jj_.arc
archive log thread 1 sequence 7 is already on disk as file /opt/oracle/flash_recovery_area1/ORCLA/archivelog/2014_08_29/o1_mf_1_7_9zz3hfff_.arc
media recovery complete, elapsed time: 00:00:01
Finished blockrecover at 29-AUG-14
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清楚坏块记录
SQL> select * from v$database_block_corruption ;
FILE# BLOCK# BLOCKS CORRUPTION_CHANGE# CORRUPTIO
---------- ---------- ---------- ------------------ ---------
5 49316 1 0 CORRUPT
RMAN> backup validate datafile 5;
Starting backup at 29-AUG-14
using channel ORA_DISK_1
using channel ORA_DISK_2
channel ORA_DISK_1: starting full datafile backupset
channel ORA_DISK_1: specifying datafile(s) in backupset
input datafile fno=00005 name=/opt/oracle/oradata/orcla/xzsp.dbf
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:03
Finished backup at 29-AUG-14
SQL> select * from v$database_block_corruption ;
no rows selected
注意：
但有些情况下,BLOCKRECOVER未必可以恢复得了:
[oracle@ique datafile]$ sqlplus mayp/mayp
SQL*Plus: Release 10.1.0.5.0 – Production on Mon Jul 14 17:08:06 2008
Copyright (c) 1982, 2005, Oracle. All rights reserved.
Connected to:
Oracle Database 10g Enterprise Edition Release 10.1.0.5.0 – Production
With the Partitioning, OLAP and Data Mining options
SQL> select count(*) from mssm;
select count(*) from mssm
*
ERROR at line 1:
ORA-01578: ORACLE data block corrupted (file # 5, block # 9)
ORA-01110: data file 5: '/data/mayp/MAYP/datafile/o1_mf_mssm_4789hznr_.dbf'
[oracle@ique datafile]$ rman target /
Recovery Manager: Release 10.1.0.5.0 – Production
Copyright (c) 1995, 2004, Oracle. All rights reserved.
connected to target database: MAYP (DBID=412172232)
RMAN> blockrecover datafile 5 block 9;
Starting blockrecover at 14-JUL-08
using target database controlfile instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: sid=378 devtype=DISK
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of blockrecover command at 07/14/2008 17:08:37
ORA-01455: converting column overflows integer datatype
RMAN-06010: error while looking up datafile: 5
这个块损坏已经严重破坏了数据的存放规律,发生了逻辑损坏,所以blockrecover没办法恢复,必须首先restore这个文件然后通过recvoer命令进行恢复.
通过常规方法恢复这个错误:
RMAN> sql 'alter database datafile 5 offline';
sql statement: alter database datafile 5 offline
RMAN> restore datafile 5;
Starting restore at 14-JUL-08
using channel ORA_DISK_1
channel ORA_DISK_1: starting datafile backupset restore
channel ORA_DISK_1: specifying datafile(s) to restore from backup set
restoring datafile 00005 to /data/mayp/MAYP/datafile/o1_mf_mssm_4789hznr_.dbf
channel ORA_DISK_1: restored backup piece 1
piece handle=/home/oracle/product/10.2/dbs/full_2_MAYP.rman tag=TAG20080714T152854
channel ORA_DISK_1: restore complete
Finished restore at 14-JUL-08
RMAN> recover datafile 5;
Starting recover at 14-JUL-08
using channel ORA_DISK_1
starting media recovery
media recovery complete
Finished recover at 14-JUL-08
RMAN> sql 'alter database datafile 5 online';
sql statement: alter database datafile 5 online
RMAN> exit
BLOCKRECOVER 的使用限制:
1、数据库必须在ARCHIVELOG模式下才可以使用这个功能;
2、数据库必须是mount或open状态;
3、不能对一个offline的datafile进行BLOCKRECOVER;
4、blcokrecover需要通过一个full backups 恢复datra block,不能使用incremental backups进行错误恢复;
5、blockrecover不能跨越archivelog丢失或损坏,也就是说在恢复的过程中,不能丢失需要的归档日志;
6、blockrecover不能恢复逻辑坏块,逻辑坏块必须首先restore损坏的数据文件,然后在用recover进行恢复;
7、blockrecvoer不能恢复file header block.(block=1).