一 不完全恢复讲解
在上一篇文章（RMAN备份与恢复之UNDO表空间丢失 ）中，我们讲到UNDO表空间丢失怎么处理。UNDO表空间是不可脱机的，同样，SYSTEM表空间也是不可脱机的，所以SYSTEM表空间丢失的处理办法和UNDO表空间丢失的处理办法类似，在此不赘述。
RMAN恢复分为完全恢复和不完全恢复。完全恢复，顾名思义，就是基于全备的基础上对数据进行恢复。但是真实环境中这样的恢复用得很少。相反，不完全恢复使用较多。不完全恢复，也就是通过备份文件，恢复某一个误操作或者是某一段时间丢失的数据。不完全恢复可以基于时间，基于SCN，基于日志序列号、基于备份控制文件。本文讲解基于时间点的不完全恢复。
二 基于时间点的不完全恢复讲解
与前面的文章一样，既然要做恢复，我们首先要有备份文件，我们使用RMAN工具对数据库进行备份。备份完全后，我们切换到SQL Plus中，打开显示完整时间的选项，为什么要显示完整时间呢？因为基于时间点的恢复需要一个时间点，打开这个选项后，一是可以使我们更方便的查看到操作过程中经历的时间，二是保证时间点选取的精确性。然后我们登录到SCOTT用户，创建一张测试表，插入数据，手动提交。注意，我们为了保证数据的一致性，最好切换到SYS用户下手动切换日志（ALTER SYSTEM SWITCH LOGFILE）和手动触发CKPT（ALTERSYSTEM CHECKPOINT）。好了，数据准备完成，我们此时删除表，并同时清空回收站，记下删除表之前的时间点，后面恢复操作要使用到。现在我们强制关闭数据库，登录到RMAN中，启动数据库到MOUNT状态，然后查看当前的INCARNATION号，至于INCARNATION号是什么东西。我们可以这样理解，每一次RESETLOGS就会使INCARNATION+1，如果想要恢复到之前INCARNATION的scn（或者时间点），就需要先跳转到之前的INCARNATION。跳转到之前的INCARNATION，我们可以使用如下命令：RESET DATABASE TO INCARNATION 。举一个不太恰当的比喻，这个INCARNATION就像我们在十字路口，此时我们不知道应该往哪个方向走，如果你一旦走错，还得回到这个十字路口选取下一条路。此时我们需要编辑恢复脚本，内容就是告诉Oracle恢复到哪个时间点，并且还原和恢复数据库。恢复完成后，我们需要使用RESETLOGS方式打开数据库，此时我们登录到SQL Plus中，查看表只中的数据，如果能够成功查询到，证明恢复成功。如果不能查询到，第一考虑时间点是否选择正确，第二确认INCARNATION号是否正确，第三数据是否保持了一致性。因为我们重置了日志，所以需要重新备份数据库。至此，完整的恢复操作完成。
三 基于时间点的恢复模拟
Step 1，SQL Plus中确保数据库在归档模式，RMAN中备份数据库
SQL> ARCHIVE LOG LIST;
Database log mode Archive Mode
Automatic archival Enabled
Archive destination USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence 68
Next log sequence to archive 70
Current log sequence 70
[oracle@orcl ~]$ uniread rman target /
[uniread] Loaded history (2 lines)
Recovery Manager: Release 11.2.0.3.0 - Production on Fri Jan 17 09:44:40 2014
Copyright (c) 1982, 2011, Oracle and/or its affiliates. All rights reserved.
connected to target database: LARRRDB (DBID=3428598070)
RMAN> BACKUP DATABASE;
Starting backup at 17-JAN-14
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=36 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=00001 name=/u01/oracle/oradata/larrrdb/system01.dbf
input datafile file number=00003 name=/u01/oracle/oradata/larrrdb/undotbs01.dbf
input datafile file number=00002 name=/u01/oracle/oradata/larrrdb/sysaux01.dbf
input datafile file number=00004 name=/u01/oracle/oradata/larrrdb/users01.dbf
channel ORA_DISK_1: starting piece 1 at 17-JAN-14
channel ORA_DISK_1: finished piece 1 at 17-JAN-14
piece handle=/u01/oracle/fast_recovery_area/LARRRDB/backupset/2014_01_17/o1_mf_nnndf_TAG20140117T094447_9fk2rhv7_.bkp tag=TAG20140117T094447 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:04:07
channel ORA_DISK_1: starting full datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
including current control file in backup set
including current SPFILE in backup set
channel ORA_DISK_1: starting piece 1 at 17-JAN-14
channel ORA_DISK_1: finished piece 1 at 17-JAN-14
piece handle=/u01/oracle/fast_recovery_area/LARRRDB/backupset/2014_01_17/o1_mf_ncsnf_TAG20140117T094447_9fk309p8_.bkp tag=TAG20140117T094447 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:03
Finished backup at 17-JAN-14
Step 2，SQL Plus中打开显示完整时间
SQL> CONN SCOTT/tiger;
Connected.
SQL> SET TIME ON;
09:53:34 SQL>
Step 3，SQL Plus创建测试表
09:53:34 SQL> CREATE TABLE test(id NUMBER(2),name VARCHAR(20));
Table created.
09:53:59 SQL>
Step 4，SQL Plus插入数据，并提交，为了保持数据一致性，最好使用sys用户手动切换日志（ALTER SYSTEM SWITCHLOGFILE）和触发CKPT（ALTERSYSTEM CHECKPOINT）
09:53:59 SQL> INSERT INTO test VALUES(1,'justdb');
1 row created.
09:54:16 SQL> COMMIT;
Commit complete.
09:54:25 SQL> SELECT * FROM test;
ID NAME
---------- --------------------
1 justdb
09:54:33 SQL>
Step 5，SQL Plus中删除测试表
09:54:33 SQL> DROP TABLE test PURGE;
Table dropped.
Step 6，SQL Plus中一致性关闭数据库
10:00:09 SQL> SHUTDOWN IMMEDIATE;
Database closed.
Database dismounted.
ORACLE instance shut down.
10:01:57 SQL>
Step 7，编辑基于时间点恢复的脚本，注意时间点的选取，此处选取为删除表的时间点（09:54:33），注意时间点尤其重要
[oracle@orcl ~]$ vim /home/oracle/recover_data_by_time.sql
[oracle@orcl ~]$ cat !$
cat /home/oracle/recover_data_by_time.sql
RUN {
SET UNTIL TIME "to_date('2014-01-17 09:54:33','yyyy-mm-dd hh24:mi:ss')";
RESTORE DATABASE;
RECOVER DATABASE;
}
Step 8，登录到RMAN，启动数据库到MOUNT状态
[oracle@orcl ~]$ uniread rman target /
[uniread] Loaded history (6 lines)
Recovery Manager: Release 11.2.0.3.0 - Production on Fri Jan 17 10:02:22 2014
Copyright (c) 1982, 2011, Oracle and/or its affiliates. All rights reserved.
connected to target database (not started)
RMAN> STARTUP MOUNT;
Oracle instance started
database mounted
Total System Global Area 839282688 bytes
Fixed Size 2233000 bytes
Variable Size 494931288 bytes
Database Buffers 339738624 bytes
Redo Buffers 2379776 bytes
Step 9，RMAN中查看当前INCARNATION号，注意：如果有其他的操作，以后恢复时应该选取当前查看到的INCARNATION号，使用RESET DATABASE TO INCARNATION 命令
RMAN> LIST INCARNATION;
using target database control file instead of recovery catalog
List of Database Incarnations
DB Key Inc Key DB Name DB ID STATUS Reset SCN Reset Time
------- ------- -------- ---------------- --- ---------- ----------
1 1 LARRRDB 3428598070 CURRENT 1 23-NOV-13
Step 10，RMAN中执行基于时间点的恢复脚本
RMAN> @ /home/oracle/recover_data_by_time.sql
@ /home/oracle/recover_data_by_time.sql
RMAN> RUN {
2> SET UNTIL TIME "to_date('2014-01-17 09:54:33','yyyy-mm-dd hh24:mi:ss')";
3> RESTORE DATABASE;
4> RECOVER DATABASE;
5> }
executing command: SET until clause
Starting restore at 17-JAN-14
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=21 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 00001 to /u01/oracle/oradata/larrrdb/system01.dbf
channel ORA_DISK_1: restoring datafile 00002 to /u01/oracle/oradata/larrrdb/sysaux01.dbf
channel ORA_DISK_1: restoring datafile 00003 to /u01/oracle/oradata/larrrdb/undotbs01.dbf
channel ORA_DISK_1: restoring datafile 00004 to /u01/oracle/oradata/larrrdb/users01.dbf
channel ORA_DISK_1: reading from backup piece /u01/oracle/fast_recovery_area/LARRRDB/backupset/2014_01_17/o1_mf_nnndf_TAG20140117T094447_9fk2rhv7_.bkp
channel ORA_DISK_1: piece handle=/u01/oracle/fast_recovery_area/LARRRDB/backupset/2014_01_17/o1_mf_nnndf_TAG20140117T094447_9fk2rhv7_.bkp tag=TAG20140117T094447
channel ORA_DISK_1: restored backup piece 1
channel ORA_DISK_1: restore complete, elapsed time: 00:04:16
Finished restore at 17-JAN-14
Starting recover at 17-JAN-14
using channel ORA_DISK_1
starting media recovery
media recovery complete, elapsed time: 00:00:01
Finished recover at 17-JAN-14
RMAN> **end-of-file**
Step 11，RMAN中使用RESETLOGS打开数据库
RMAN> ALTER DATABASE OPEN RESETLOGS;
database opened
Step 12，SQL Plus中查看数据，如果能够正确地查看到，证明恢复成功
[oracle@orcl ~]$ sqlplus
[uniread] Loaded history (66 lines)
SQL*Plus: Release 11.2.0.3.0 Production on Fri Jan 17 10:10:53 2014
Copyright (c) 1982, 2011, Oracle. All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
With the Partitioning, Oracle Label Security, OLAP, Data Mining,
Oracle Database Vault and Real Application Testing options
SQL> SELECT open_mode FROM v$database;
OPEN_MODE
--------------------
READ WRITE
#这正是被删除掉的表中的数据
SQL> SELECT * FROM scott.test;
ID NAME
---------- --------------------
1 justdb
Step 13，因为重置了日志，我们需要重新在RMAN中备份
[oracle@orcl ~]$ uniread rman target /
[uniread] Loaded history (2 lines)
Recovery Manager: Release 11.2.0.3.0 - Production on Fri Jan 17 09:44:40 2014
Copyright (c) 1982, 2011, Oracle and/or its affiliates. All rights reserved.
connected to target database: LARRRDB (DBID=3428598070)
RMAN> BACKUP DATABASE;
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