无RMAN备份集情况下的坏块恢复 - 数据库编程

SQL> conn zlm/zlm
Connected.
SQL> select * from corrupt_test;

? ? ? ? ID NAME
---------- ---------------
? ? ? ? 1 aaron8219

此时由于测试表corrupt_test里数据块中的行数据还在内存中，所以还是可以查询到行记录的

SQL> alter system flush buffer_cache;

System altered.

SQL> select * from corrupt_test;
select * from corrupt_test
? ? ? ? ? ? ? *
ERROR at line 1:
ORA-01578: ORACLE data block corrupted (file # 6, block # 12)
ORA-01110: data file 6: '/u01/app/oracle/oradata/ora10g/zlm01.dbf'

但是一旦我们把它刷到磁盘，就报ORA-01578的错误了，提示6号文件的第12个块损坏了，就是之前指定的那个数据块

SQL> exit
Disconnected from Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production
With the Partitioning, OLAP and Data Mining options
[oracle@ora10g backupsets]$ rman target /

Recovery Manager: Release 10.2.0.1.0 - Production on 16 16:30:19 2014

connected to target database: ORA10G (DBID=4175411955)

RMAN> blockrecover datafile 6 block 12;

Starting blockrecover at 2014-11-26
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: sid=159 devtype=DISK

RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of blockrecover command at 11/26/2014 16:30:51
RMAN-06026: some targets not found - aborting restore
RMAN-06023: no backup or copy of datafile 6 found to restore

此时直接用blockrecover来恢复坏块是不行的，首先我们没有可用的备份集，其次，控制文件中也不知道从哪里去找可用的备份文件，那么我们就要先把之前做过的热备文件catalog到控制文件中

RMAN> catalog datafilecopy '/u01/zlm01_bak.dbf';

cataloged datafile copy
datafile copy filename=/u01/zlm01_bak.dbf recid=17 stamp=864664486

RMAN> blockrecover datafile 6 block 12;

Starting blockrecover at 2014-11-26
using channel ORA_DISK_1

channel ORA_DISK_1: restoring block(s) from datafile copy /u01/zlm01_bak.dbf

starting media recovery
media recovery complete, elapsed time: 00:00:01

Finished blockrecover at 2014-11-26

RMAN> exit

Recovery Manager complete.

再做一次blockrecover，现在就顺利地介质恢复完了

[oracle@ora10g backupsets]$ sqlplus zlm/zlm

SQL*Plus: Release 10.2.0.1.0 - Production on 16 16:35:23 2014

Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production
With the Partitioning, OLAP and Data Mining options

SQL> select * from corrupt_test;

? ? ? ? ID NAME
---------- ---------------
? ? ? ? 1 aaron8219

SQL>

可以看到，之前丢失的数据，又回来了

总结：

虽然在没有RMAN备份集的情况下，通过热备文件可以把丢失的数据恢复出来，但这毕竟还是很不靠谱的。在生产环境中，我们几乎不可能经常去对某个数据文件做热备，也不会知道什么时候，哪个文件就会出现坏块。所以，平时做好RMAN全备还是非常非常重要的，只要有备份集和归档，我们的数据就不会丢失。当执行blockrecover datafile xxx block xxx时，Oracle会直接去RMAN备份集中恢复，不需要额外的catalog步骤，也不用我们过多地人为干预。

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无RMAN备份集情况下的坏块恢复(五)