4.3丢失多个数据文件，实现整个数据库的恢复.
4.3.1 OS备份方案
OS备份归档模式下损坏（丢失）多个数据文件，进行整个数据库的恢复
1、 连接数据库，创建测试表并插入记录
SQL> connect internal/password as sysdba;
Connected.
SQL> create table test(a int);
Table created
SQL> insert into test values(1);
1 row inserted
SQL> commit;
Commit complete
2、 备份数据库，备份除临时数据文件后的所数据文件
SQL> @hotbak.sql 或在DOS下 svrmgrl @hotbak.sql
3、 继续在测试表中插入记录
SQL> insert into test values(2);
1 row inserted
SQL> commit;
Commit complete
SQL> select * from test;
A
---------------------------------------
1
2
SQL> alter system switch logfile;
System altered.
SQL> alter system switch logfile;
System altered.
4、 关闭数据库，模拟丢失数据文件
SQL> shutdown immediate;
Database closed.
Database dismounted.
Oracle instance shut down
C:\>del D:\Oracle\ORADATA\TEST\SYSTEM01.DBF
C:\>del D:\Oracle\ORADATA\TEST\INDX01.DBF
C:\>del D:\Oracle\ORADATA\TEST\TOOLS01.DBF
C:\>del D:\Oracle\ORADATA\TEST\RBS01.DBF
模拟媒体毁坏（这里删除多个数据文件）
5、 启动数据库，检查错误
SQL> STARTUP
Oracle instance started.
Total System Global Area 102020364 bytes
Fixed Size 70924 bytes
Variable Size 85487616 bytes
Database Buffers 16384000 bytes
Redo Buffers 77824 bytes
Database mounted.
ORA-01157: cannot identify/lock data file 1 - see DBWR trace file
ORA-01110: data file 1: 'D:\Oracle\ORADATA\TEST\SYSTEM01.DBF'
详细信息可以查看报警文件
ORA-1157 signalled during: ALTER DATABASE OPEN...
Thu May 08 09:39:36 2003
Errors in file D:\Oracle\admin\test\bdump\testDBW0.TRC:
ORA-01157: cannot identify/lock data file 1 - see DBWR trace file
ORA-01110: data file 1: 'D:\Oracle\ORADATA\TEST\SYSTEM01.DBF'
ORA-27041: unable to open file
OSD-04002: unable to open file
O/S-Error: (OS 2) 系统找不到指定的文件。
Thu May 08 09:39:36 2003
Errors in file D:\Oracle\admin\test\bdump\testDBW0.TRC:
ORA-01157: cannot identify/lock data file 2 - see DBWR trace file
ORA-01110: data file 2: 'D:\Oracle\ORADATA\TEST\RBS01.DBF'
ORA-27041: unable to open file
OSD-04002: unable to open file
O/S-Error: (OS 2) 系统找不到指定的文件。
Thu May 08 09:39:36 2003
Errors in file D:\Oracle\admin\test\bdump\testDBW0.TRC:
ORA-01157: cannot identify/lock data file 5 - see DBWR trace file
ORA-01110: data file 5: 'D:\Oracle\ORADATA\TEST\TOOLS01.DBF'
ORA-27041: unable to open file
OSD-04002: unable to open file
O/S-Error: (OS 2) 系统找不到指定的文件。
Thu May 08 09:39:36 2003
Errors in file D:\Oracle\admin\test\bdump\testDBW0.TRC:
ORA-01157: cannot identify/lock data file 6 - see DBWR trace file
ORA-01110: data file 6: 'D:\Oracle\ORADATA\TEST\INDX01.DBF'
ORA-27041: unable to open file
OSD-04002: unable to open file
O/S-Error: (OS 2) 系统找不到指定的文件。
通过查询v$recover_file可以看到
SQL> select * from v$recover_file;
FILE# ONLINE ERROR CHANGE# TIME
---------- ------- ------------------ ---------- -----------
1 ONLINE FILE NOT FOUND 0
2 ONLINE FILE NOT FOUND 0
5 ONLINE FILE NOT FOUND 0
6 ONLINE FILE NOT FOUND 0
有四个数据文件需要恢复
6、 拷贝备份回到原地点(restore)，开始恢复数据库(recover)
restore过程:
C:\>copy D:\DATABAK\SYSTEM01.DBF D:\Oracle\ORADATA\TEST\
C:\>copy D:\DATABAK\TEST\INDX01.DBF D:\Oracle\ORADATA\TEST\
C:\>copy D:\DATABAK\TEST\TOOLS01.DBF D:\Oracle\ORADATA\TEST\
C:\>copy D:\DATABAK\TEST\RBS01.DBF.DBF D:\Oracle\ORADATA\TEST\
Recover过程:
SQL> recover database;
ORA-00279: change 1073849 generated at 05/08/2003 08:58:35 needed for thread 1
ORA-00289: suggestion : D:\Oracle\ORADATA\TEST\ARCHIVE\TESTT001S00311.ARC
ORA-00280: change 1073849 for thread 1 is in sequence #311
Specify log: {=suggested | filename | AUTO | CANCEL}
auto
ORA-00279: change 1073856 generated at 05/08/2003 09:03:27 needed for thread 1
ORA-00289: suggestion : D:\Oracle\ORADATA\TEST\ARCHIVE\TESTT001S00312.ARC
ORA-00280: change 1073856 for thread 1 is in sequence #312
ORA-00278: log file 'D:\Oracle\ORADATA\TEST\ARCHIVE\TESTT001S00311.ARC' no
longer needed for this recovery
ORA-00279: change 1073858 generated at 05/08/2003 09:11:43 needed for thread 1
ORA-00289: suggestion : D:\Oracle\ORADATA\TEST\ARCHIVE\TESTT001S00313.ARC
ORA-00280: change 1073858 for thread 1 is in sequence #313
ORA-00278: log file 'D:\Oracle\ORADATA\TEST\ARCHIVE\TESTT001S00312.ARC' no
longer needed for this recovery
ORA-00279: change 1073870 generated at 05/08/2003 09:11:46 needed for thread 1
ORA-00289: suggestion : D:\Oracle\ORADATA\TEST\ARCHIVE\TESTT001S00314.ARC
ORA-00280: change 1073870 for thread 1 is in sequence #314
ORA-00278: log file 'D:\Oracle\ORADATA\TEST\ARCHIVE\TESTT001S00313.ARC' no
longer needed for this recovery
Log applied.
Media recovery complete.
7、 打开数据库，检查数据库的数据（完全恢复）
SQL> alter database open;
Database altered.
SQL> select * from test;
A
---------------------------------------
1
2
说明：
1、只要有备份与归档存在，就可以实现数据库的完全恢复（不丢失数据）;
2、适合于丢失大量数据文件，或包含系统数据文件在内的数据库的恢复;
3、恢复过程在mount下进行，如果恢复成功，再打开数据库，down机时间可能比较长一些。
4.3.2 RMAN备份方案
RMAN备份归档模式下损坏（丢失）多个数据文件，进行整个数据库的恢复
1、连接数据库，创建测试表并插入记录
SQL> connect internal/password as sysdba;
Connected.
SQL> create table test(a int);
Table created
SQL> insert into test values(1);
1 row inserted
SQL> commit;
Commit complete
2、备份数据库
DOS下 C:>\ rman cmdfile=bakup.rcv msglog=backup.log;
以下是backup.log内容。
Recovery Manager: Release 8.1.6.0.0 - Production
RMAN> # script:bakup.rcv
2> # creater:chenjiping
3> # date:5.8.2003
4> # desc:backup all database datafile in archive with rman
5>
6> #connect database
7> connect rcvcat rman/rman@back;
8> connect target internal/virpure;
9>
10> #start backup database
11> run{
12> allocate channel c1 type disk;
13> backup full tag 'dbfull' format 'd:\backup\full%u_%s_%p' database
14> include current controlfile;
15> sql 'alter system archive log current';
16> release channel c1;
17> }
18> #end
19>
RMAN-06008: connected to recovery catalog database
RMAN-06005: connected to target database: TEST (DBID=1788174720)
RMAN-03022: compiling command: allocate
RMAN-03023: executing command: allocate
RMAN-08030: allocated channel: c1
RMAN-08500: channel c1: sid=15 devtype=DISK
RMAN-03022: compiling command: backup
RMAN-03023: executing command: backup
RMAN-08008: channel c1: starting full datafile backupset
RMAN-08502: set_count=4 set_stamp=494074368 creation_time=15-MAY-03
RMAN-08010: channel c1: specifying datafile(s) in backupset
RMAN-08522: input datafile fno=00002 name=D:\Oracle\ORADATA\TEST\RBS01.DBF
RMAN-08522: input datafile fno=00001 name=D:\Oracle\ORADATA\TEST\SYSTEM01.DBF
RMAN-08011: including current controlfile in backupset
RMAN-08522: input datafile fno=00005 name=D:\Oracle\ORADATA\TEST\TOOLS01.DBF
RMAN-08522: input datafile fno=00004 name=D:\Oracle\ORADATA\TEST\TEMP01.DBF
RMAN-08522: input datafile fno=00006 name=D:\Oracle\ORADATA\TEST\INDX01.DBF
RMAN-08522: input datafile fno=00003 name=D:\Oracle\ORADATA\TEST\USER01.DBF
RMAN-08013: channel c1: piece 1 created
RMAN-08503: piece handle=D:\BACKUP\FULL04EN5UG0_4_1 comment=NONE
RMAN-08525: backup set complete, elapsed time: 00:01:16
RMAN-03023: executing command: partial resync
RMAN-08003: starting partial resync of recovery catalog
RMAN-08005: partial resync complete
RMAN-03022: compiling command: sql
RMAN-06162: sql statement: alter system archive log current
RMAN-03023: executing command: sql
RMAN-03022: compiling command: release
RMAN-03023: executing command: release
RMAN-08031: released channel: c1
Recovery Manager complete.
到这里表示备份成功。
3、 继续在测试表中插入记录
SQL> insert into test values(2);
1 row inserted
SQL> commit;
Commit complete
SQL> select * from test;
A
---------------------------------------
1
2
SQL>alter system switch logfile;
System altered.
SQL> alter system switch logfile;
System altered.
4、 关闭数据库，模拟丢失数据文件
SQL> shutdown immediate;
Database closed.
Database dismounted.
Oracle instance shut down
C:\>del D:\Oracle\ORADATA\TEST\SYSTEM01.DBF
C:\>del D:\Oracle\ORADATA\TEST\INDX01.DBF
C:\>del D:\Oracle\ORADATA\TEST\TOOLS01.DBF
C:\>del D:\Oracle\ORADATA\TEST\RBS01.DBF
5、启动数据库，检查错误
SQL> STARTUP
Oracle instance started.
Total System Global Area 102020364 bytes
Fixed Size 70924 bytes
Variable Size 85487616 bytes
Database Buffers 16384000 bytes
Redo Buffers 77824 bytes
Database mounted.
ORA-01157: cannot identify/lock data file 1 - see DBWR trace file
ORA-01110: data file 1: 'D:\Oracle\ORADATA\TEST\SYSTEM01.DBF'
查询v$recover_file
SQL> select * from v$recover_file;
FILE# ONLINE ERROR CHANGE# TIME
---------- ------- ------------------ ---------- -----------
1 ONLINE FILE NOT FOUND 0
2 ONLINE FILE NOT FOUND 0
5 ONLINE FILE NOT FOUND 0
6 ONLINE FILE NOT FOUND 0
可以知道有四个数据文件需要恢复.
6、利用RMAN进行恢复
C:\>rman
Recovery Manager: Release 8.1.6.0.0 - Production
RMAN> connect rcvcat rman/rman@back
RMAN-06008: connected to recovery catalog database
RMAN> connect target internal/virpure
RMAN-06005: connected to target database: TEST (DBID=1788174720)
RMAN> run{
2> allocate channel c1 type disk;
3> restore database;
4> recover database;
5> sql 'alter database open';
6> release channel c1;
7> }
RMAN-03022: compiling command: allocate
RMAN-03023: executing command: allocate
RMAN-08030: allocated channel: c1
RMAN-08500: channel c1: sid=17 devtype=DISK
RMAN-03022: compiling command: restore
RMAN-03025: performing implicit partial resync of recovery catalog
RMAN-03023: executing command: partial resync
RMAN-08003: starting partial resync of recovery catalog
RMAN-08005: partial resync complete
RMAN-03022: compiling command: IRESTORE
RMAN-03023: executing command: IRESTORE
RMAN-08016: channel c1: starting datafile backupset restore
RMAN-08502: set_count=4 set_stamp=494074368 creation_time=15-MAY-03
RMAN-08089: channel c1: specifying datafile(s) to restore from backup set
RMAN-08523: restoring datafile 00001 to D:\Oracle\ORADATA\TEST\SYSTEM01.DBF
RMAN-08523: restoring datafile 00002 to D:\Oracle\ORADATA\TEST\RBS01.DBF
RMAN-08523: restoring datafile 00003 to D:\Oracle\ORADATA\TEST\USER01.DBF
RMAN-08523: restoring datafile 00004 to D:\Oracle\ORADATA\TEST\TEMP01.DBF
RMAN-08523: restoring datafile 00005 to D:\Oracle\ORADATA\TEST\TOOLS01.DBF
RMAN-08523: restoring datafile 00006 to D:\Oracle\ORADATA\TEST\INDX01.DBF
RMAN-08023: channel c1: restored backup piece 1
RMAN-08511: piece handle=D:\BACKUP\FULL04EN5UG0_4_1 tag=DBFULL params=NULL
RMAN-08024: channel c1: restore complete
RMAN-03023: executing command: partial resync
RMAN-08003: starting partial resync of recovery catalog
RMAN-08005: partial resync complete
RMAN-03022: compiling command: recover
RMAN-03022: compiling command: recover(1)
RMAN-03022: compiling command: recover(2)
RMAN-03022: compiling command: recover(3)
RMAN-03023: executing command: recover(3)
RMAN-08054: starting media recovery
RMAN-03022: compiling command: recover(4)
RMAN-06050: archivelog thread 1 sequence 327 is already on disk as file D:\Oracle\ORADATA\TEST\ARCHIVE\TESTT001S00327.ARC
RMAN-06050: archivelog thread 1 sequence 328 is already on disk as file D:\Oracle\ORADATA\TEST\ARCHIVE\TESTT001S00328.ARC
RMAN-06050: archivelog thread 1 sequence 329 is already on disk as file D:\Oracle\ORADATA\TEST\ARCHIVE\TESTT001S00329.ARC
RMAN-06050: archivelog thread 1 sequence 330 is already on disk as file D:\Oracle\ORADATA\TEST\ARCHIVE\TESTT001S00330.ARC
RMAN-03023: executing command: recover(4)
RMAN-08515: archivelog filename=D:\Oracle\ORADATA\TEST\ARCHIVE\TESTT001S00327.ARC thread=1 sequence=327
RMAN-08515: archivelog filename=D:\Oracle\ORADATA\TEST\ARCHIVE\TESTT001S00328.ARC thread=1 sequence=328
RMAN-08055: media recovery complete
RMAN-03022: compiling command: sql
RMAN-06162: sql statement: alter database open
RMAN-03023: executing command: sql
RMAN-03022: compiling command: release
RMAN-03023: executing command: release
RMAN-08031: released channel: c1
RMAN>
7、 检查数据库的数据（完全恢复）
SQL> select * from test;
A
---------------------------------------
1
2
说明：
1、只要有备份与归档存在，RMAN也可以实现数据库的完全恢复（不丢失数据）;
2、同OS备份数据库恢复，适合于丢失大量数据文件，或包含系统数据文件在内的数据库的恢复;
3、目标数据库在mount下进行，如果恢复成功，再打开数据库;
4、RMAN的备份与恢复命令相对比较简单并可靠，建议有条件的话，都采用RMAN进行数据库的备份。
4.4 不完全恢复案例
4.4.1 OS备份下的基于时间的恢复
不完全恢复可以分为基于时间的恢复，基于改变的恢复与基于撤消的恢复，这里已基于时间的恢复为例子来说明不完全恢复过程。
基于时间的恢复可以不完全恢复到现在时间之前的某一个时间，对于某些误操作，如删除了一个数据表，可以在备用恢复环境上恢复到表的删除时间之前，然后把该表导出到正式环境，避免一个人为的错误。
1、 连接数据库，创建测试表并插入记录:
SQL> connect internal/password as sysdba;
Connected.
SQL> create table test(a int);
Table created
SQL> insert into test values(1);
1 row inserted
SQL> commit;
Commit complete
2、 备份数据库，这里最好备份所有的数据文件，包括临时数据文件:
SQL> @hotbak.sql 或在DOS下 svrmgrl @hotbak.sql
或冷备份也可以
3、 删除测试表，假定删除前的时间为T1，在删除之前，便于测试，继续插入数据并应用到归
档。
SQL> insert into test values(2);
1 row inserted
SQL> commit;
Commit complete
SQL> select * from test;
A
---------------------------------------
1
2
SQL> alter system switch logfile;
Statement processed.
SQL> alter system switch logfile;
Statement processed.
SQL> select to_char(sysdate,'yyyy-mm-dd hh24:mi:ss') from dual;
TO_CHAR(SYSDATE,'YY
-------------------
2003-05-21 14:43:01
SQL> drop table test;
Table dropped.
4、 准备恢复到时间点T1，找回删除的表，先关闭数据库:
SQL> shutdown immediate;
Database closed.
Database dismounted.
Oracle instance shut down.
5、 拷贝刚才备份的所有数据文件回来
C:\>copy D:\DATABAK\*.DBF D:\Oracle\ORADATA\TEST\
6、 启动到mount下
SQL> startup mount;
Oracle instance started.
Total System Global Area 102020364 bytes
Fixed Size 70924 bytes
Variable Size 85487616 bytes
Database Buffers 16384000 bytes
Redo Buffers 77824 bytes
Database mounted.
7、 开始不完全恢复数据库到T1时间
SQL> recover database until time '2003-05-21:14:43:01';
ORA-00279: change 30944 generated at 05/21/2003 14:40:06 needed for thread 1
ORA-00289: suggestion : D:\Oracle\ORADATA\TEST\ARCHIVE\TESTT001S00191.ARC
ORA-00280: change 30944 for thread 1 is in sequence #191
Specify log: {=suggested | filename | AUTO | CANCEL}
auto
Log applied.
Media recovery complete.
8、 打开数据库，检查数据
SQL> alter database open resetlogs;
Database altered.
SQL> select * from test;
A
---------------------------------------
1
2
说明：
1、不完全恢复最好备份所有的数据，冷备份亦可，因为恢复过程是从备份点往后恢复的，如果因为其中一个数据文件的时间戳(SCN)大于要恢复的时间点，那么恢复都是不可能成功的;
2、不完全恢复有三种方式，过程都一样，仅仅是recover命令有所不一样，这里用基于时间的恢复作为示例;
3、不完全恢复之后，都必须用resetlogs的方式打开数据库，建议马上再做一次全备份，因为resetlogs之后再用以前的备份恢复是很难了;
4、以上是在删除之前获得时间，但是实际应用中，很难知道删除之前的实际时间，但可以采用大致时间即可，或可以采用分析日志文件(logmnr)，取得精确的需要恢复的时间;
5、一般都是在测试机后备用机器上采用这种不完全恢复，恢复之后导出/导入被误删的表回生产系统.
4.4.2 RMAN备份下的基于改变的恢复
以上用OS备份说明了一个基于时间的恢复，现在用RMAN说明一个基于改变的恢复
1、 连接数据库，创建测试表并插入记录
SQL> connect internal/password as sysdba;
Connected.
SQL> create table test(a int);
Table created
SQL> insert into test values(1);
1 row inserted
SQL> commit;
Commit complete
2、 备份数据库
C:\>rman
Recovery Manager: Release 8.1.6.0.0 - Production
RMAN> connect rcvcat rman/rman@back
RMAN-06008: connected to recovery catalog database
RMAN> connect target internal/virpure
RMAN-06005: connected to target database: TEST (DBID=874705288)
RMAN> run{
2> allocate channel c1 type disk;
3> backup full tag 'dbfull' format 'd:\backup\full%u_%s_%p' database
4> include current controlfile;
5> sql 'alter system archive log current';
6> release channel c1;
7> }
//屏幕输出内容冗长，省略--编辑
RMAN>
3、 删除测试表，在删除之前，便于测试，继续插入数据并应用到归档，并获取删除前的scn号。
SQL> insert into test values(2);
1 row inserted
SQL> commit;
Commit complete
SQL> select * from test;
A
---------------------------------------
1
2
SQL> alter system switch logfile;
Statement processed.
SQL> alter system switch logfile;
Statement processed.
SQL> select max(ktuxescnw * power(2, 32) + ktuxescnb) scn from x$ktuxe;
SCN
----------
31014
SQL> drop table test;
Table dropped.
4、 准备恢复到SCN 31014，先关闭数据库，然后启动到mount下
SQL> shutdown immediate;
Database closed.
Database dismounted.
Oracle instance shut down.
SQL> startup mount;
5、 开始恢复到改变点SCN 31014
RMAN> run{
2> allocate channel c1 type disk;
3> restore database;
4> recover database until scn 31014;
5> sql 'ALTER DATABASE OPEN RESETLOGS';
6> release channel c1;
7> }
RMAN-03022: compiling command: allocate
RMAN-03023: executing command: allocate
RMAN-08030: allocated channel: c1
RMAN-08500: channel c1: sid=10 devtype=DISK
RMAN-03022: compiling command: restore
RMAN-03022: compiling command: IRESTORE
RMAN-03023: executing command: IRESTORE
RMAN-08016: channel c1: starting datafile backupset restore
RMAN-08502: set_count=1 set_stamp=494613682 creation_time=21-MAY-03
RMAN-08089: channel c1: specifying datafile(s) to restore from backup set
RMAN-08523: restoring datafile 00001 to D:\Oracle\ORADATA\TEST\SYSTEM01.DBF
RMAN-08523: restoring datafile 00002 to D:\Oracle\ORADATA\TEST\RBS01.DBF
RMAN-08523: restoring datafile 00003 to D:\Oracle\ORADATA\TEST\USERS01.DBF
RMAN-08523: restoring datafile 00004 to D:\Oracle\ORADATA\TEST\TEMP01.DBF
RMAN-08523: restoring datafile 00005 to D:\Oracle\ORADATA\TEST\TOOLS01.DBF
RMAN-08523: restoring datafile 00006 to D:\Oracle\ORADATA\TEST\INDX01.DBF
RMAN-08023: channel c1: restored backup piece 1
RMAN-08511: piece handle=D:\BACKUP\FULL01ENMD5I_1_1 tag=DBFULL params=NULL
RMAN-08024: channel c1: restore complete
RMAN-03023: executing command: partial resync
RMAN-08003: starting partial resync of recovery catalog
RMAN-08005: partial resync complete
RMAN-03022: compiling command: recover
RMAN-03022: compiling command: recover(1)
RMAN-03022: compiling command: recover(2)
RMAN-03022: compiling command: recover(3)
RMAN-03023: executing command: recover(3)
RMAN-08054: starting media recovery
RMAN-03022: compiling command: recover(4)
RMAN-06050: archivelog thread 1 sequence 191 is already on disk as file D:\ORACL
E\ORADATA\TEST\ARCHIVE\TESTT001S00191.ARC
RMAN-06050: archivelog thread 1 sequence 192 is already on disk as file D:\ORACL
E\ORADATA\TEST\ARCHIVE\TESTT001S00192.ARC
RMAN-03023: executing command: recover(4)
RMAN-08515: archivelog filename=D:\Oracle\ORADATA\TEST\ARCHIVE\TESTT001S00191.AR
C thread=1 sequence=191
RMAN-08515:archivelog filename=D:\Oracle\ORADATA\TEST\ARCHIVE\TESTT001S00192.ARC
Thread=1 sequence=192
RMAN-08055: media recovery complete
RMAN-03022: compiling command: sql
RMAN-06162: sql statement: ALTER DATABASE OPEN RESETLOGS
RMAN-03023: executing command: sql
RMAN-03022: compiling command: release
RMAN-03023: executing command: release
RMAN-08031: released channel: c1
6、 检查数据
Database altered.
SQL> select * from test;
A
---------------------------------------
1
2
可以看到，表依然存在。
说明：
1、 RMAN也可以实现不完全恢复，方法比OS备份恢复的方法更简单可靠；
2、 RMAN可以基于时间，基于改变与基于日志序列的不完全恢复，基于日志序列的恢复可以指定恢复到哪个日志序列，如
run {
allocate channel ch1 type disk;
allocate channel ch2 type 'sbt_tape';
set until logseq 1234 thread 1;
restore controlfile to '$Oracle_HOME/dbs/cf1.f' ;
replicate controlfile from '$Oracle_HOME/dbs/cf1.f';
alter database mount;
restore database;
recover database;
sql "ALTER DATABASE OPEN RESETLOGS";
}
3、 与所有的不完全恢复一样，必须在mount下，restore所有备份数据文件，需要resetlogs；
4、 基于改变的恢复比基于时间的恢复更可靠，但是可能也更复杂，需要知道需要恢复到哪一个改变号(SCN)，在正常生产中，获取SCN的办法其实也有很多，如查询数据库字典表(V$archived_log or v$log_history)，或分析归档与联机日志(logmnr)等。
