不可恢复的NOLOGGING 数据库对象
1) 备份users表空间
[Oracle@ocmu ~]$ rman target /
Recovery Manager: Release 11.2.0.1.0 - Production on Sat Mar 16 10:41:05 2013
Copyright (c) 1982, 2009, Oracle and/or its affiliates. All rights reserved.
connected to target database: ORA11GR2 (DBID=116453860)
RMAN> backup as backupset tablespace users;
Starting backup at 16-MAR-13
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=41 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=/u01/app/oracle/oradata/ORA11GR2/users01.dbf
channel ORA_DISK_1: starting piece 1 at 16-MAR-13
channel ORA_DISK_1: finished piece 1 at 16-MAR-13
piece handle=/u01/app/FRA/ORA11GR2/backupset/2013_03_16/o1_mf_nnndf_TAG20130316T104134_8n7pyymv_.bkp tag=TAG20130316T104134 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:05
Finished backup at 16-MAR-13
Starting Control File and SPFILE Autobackup at 16-MAR-13
piece handle=/u01/app/FRA/ORA11GR2/autobackup/2013_03_16/o1_mf_s_810211299_8n7pz48h_.bkp comment=NONE
Finished Control File and SPFILE Autobackup at 16-MAR-13
RMAN>
2) 采用nologging属性创建表，并且以直接路径加载的方式插入数据
SCOTT@ORA11GR2>create table t_objects nologging tablespace users as select * from all_objects where 1=2;
Table created.
SCOTT@ORA11GR2>insert /*+ append */ into t_objects select * from all_objects;
55641 rows created.
SCOTT@ORA11GR2>commit;
Commit complete.
SCOTT@ORA11GR2>
3) RMAN中列出包含不可恢复数据的数据文件
RMAN> report unrecoverable database;
Report of files that need backup due to unrecoverable operations
File Type of Backup Required Name
---- ----------------------- --------------------------------------------
4 full or incremental /u01/app/oracle/oradata/ORA11GR2/users01.dbf
RMAN>
4) 删除users表空间，测试nologging的不可恢复性
SYS@ORA11GR2>select file_name from dba_data_files where tablespace_name='USERS';
FILE_NAME
--------------------------------------------------------------------------
/u01/app/oracle/oradata/ORA11GR2/users01.dbf
SYS@ORA11GR2>!ls /u01/app/oracle/oradata/ORA11GR2/users01.dbf
/u01/app/oracle/oradata/ORA11GR2/users01.dbf
SYS@ORA11GR2>!rm /u01/app/oracle/oradata/ORA11GR2/users01.dbf
SYS@ORA11GR2>!ls /u01/app/oracle/oradata/ORA11GR2/users01.dbf
ls: /u01/app/oracle/oradata/ORA11GR2/users01.dbf: No such file or directory
SYS@ORA11GR2>
5) RMAN执行恢复users表空间操作
RMAN> shutdown immediate;
database closed
database dismounted
Oracle instance shut down
RMAN> startup mount;
connected to target database (not started)
Oracle instance started
database mounted
Total System Global Area 841162752 bytes
Fixed Size 1339768 bytes
Variable Size 578817672 bytes
Database Buffers 255852544 bytes
Redo Buffers 5152768 bytes
RMAN> restore tablespace users;
Starting restore at 16-MAR-13
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=18 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 /u01/app/oracle/oradata/ORA11GR2/users01.dbf
channel ORA_DISK_1: reading from backup piece /u01/app/FRA/ORA11GR2/backupset/2013_03_16/o1_mf_nnndf_TAG20130316T104134_8n7pyymv_.bkp
channel ORA_DISK_1: piece handle=/u01/app/FRA/ORA11GR2/backupset/2013_03_16/o1_mf_nnndf_TAG20130316T104134_8n7pyymv_.bkp tag=TAG20130316T104134
channel ORA_DISK_1: restored backup piece 1
channel ORA_DISK_1: restore complete, elapsed time: 00:00:08
Finished restore at 16-MAR-13
RMAN> recover tablespace users;
Starting recover at 16-MAR-13
using channel ORA_DISK_1
starting media recovery
media recovery complete, elapsed time: 00:00:01
Finished recover at 16-MAR-13
RMAN> alter database open;
database opened
RMAN>
6) 验证NOLOGGING的不可恢复性
SCOTT@ORA11GR2>select count(*) from t_objects;
select count(*) from t_objects
*
ERROR at line 1:
ORA-01578: ORACLE data block corrupted (file # 4, block # 675)
ORA-01110: data file 4: '/u01/app/oracle/oradata/ORA11GR2/users01.dbf'
ORA-26040: Data block was loaded using the NOLOGGING option
SCOTT@ORA11GR2>
7) 小结
NOLONGGING能让你“一时之快”，但是风险是极大的，所以要尽快备份或在空闲时间重建表。
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