只要存在有效的备份，恢复SYSTEM表空间数据文件丢失故障是比较容易的。这里演示的是最基本的使用物理备份恢复SYSTEM表空间丢失的方法。
1.环境准备
我们在Oracle11g中进行测试，数据库处于非归档状态。
SQL>
SQL> select * from v$version;
BANNER
--------------------------------------------------------------------------------
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - Production
PL/SQL Release 11.2.0.3.0 - Production
CORE 11.2.0.3.0 Production
TNS for Linux: Version 11.2.0.3.0 - Production
NLSRTL Version 11.2.0.3.0 - Production
SQL>
SQL> archive log list;
Database log mode No Archive Mode
Automatic archival Disabled
Archive destination /u01/app/oracle/product/11.2.0/dbhome_1/dbs/arch
Oldest online log sequence 6
Current log sequence 8
SQL>
2.打tar包，进行物理备份
首先要弄清两个概念：打包和压缩。打包是指将一大堆文件或目录变成一个总的文件；压缩则是将一个大的文件通过一些压缩算法变成一个小文件。linux下最常用的打包程序就是tar了，使用tar程序打出来的包我们常称为tar包，tar包文件的命令通常都是以.tar结尾的。生成tar包后，就可以用其它的程序来进行压缩。
我们使用tar命令将HOEGH数据库的物理文件打tar包，命名为HOEGH.tar.gz。注意，物理备份必须是在数据库关停阶段进行。
[oracle@hoegh oradata]$ tar -zcvf HOEGH.tar.gz HOEGH
HOEGH/
HOEGH/redo03.log
HOEGH/temp01.dbf
HOEGH/control01.ctl
HOEGH/control02.ctl
HOEGH/system01.dbf
HOEGH/sysaux01.dbf
HOEGH/users01.dbf
HOEGH/undotbs01.dbf
HOEGH/example01.dbf
HOEGH/redo02.log
HOEGH/redo01.log
3.启动数据库，删除system数据文件
下面，我们来模拟system数据文件丢失的故障场景。
首先，启动数据库。
SQL> startup
ORACLE instance started.
Total System Global Area 941600768 bytes
Fixed Size 1348860 bytes
Variable Size 515902212 bytes
Database Buffers 419430400 bytes
Redo Buffers 4919296 bytes
Database mounted.
Database opened.
SQL>
接下来，删除system01.dbf数据文件。
[oracle@hoegh HOEGH]$ rm system01.dbf
[oracle@hoegh HOEGH]$
4.重启数据库报错ORA-01157和ORA-01110
删除数据文件后，我们重启数据库，数据库在尝试启动到open状态时，由于找不到system表空间的数据文件，报错。
SQL>
SQL> shu immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL>
SQL> startup
ORACLE instance started.
Total System Global Area 941600768 bytes
Fixed Size 1348860 bytes
Variable Size 515902212 bytes
Database Buffers 419430400 bytes
Redo Buffers 4919296 bytes
Database mounted.
ORA-01157: cannot identify/lock data file 1 - see DBWR trace file
ORA-01110: data file 1: \'/u01/app/oracle/oradata/HOEGH/system01.dbf\'
SQL>
SQL> select status from v$instance;
STATUS
------------
MOUNTED
SQL>
我们看到，这个时候数据库处于mount状态。查看报警日志文件，我们可以更清晰的看到整个过程。
[oracle@hoegh trace]$ pwd
/u01/app/oracle/diag/rdbms/HOEGH/HOEGH/trace
[oracle@hoegh trace]$
[oracle@hoegh trace]$ tailf alert_HOEGH.log
……
ALTER DATABASE MOUNT
Successful mount of redo thread 1, with mount id 2106090167
Database mounted in Exclusive Mode
Lost write protection disabled
Completed: ALTER DATABASE MOUNT
Sat Jul 11 09:01:47 2015
ALTER DATABASE OPEN
Errors in file /u01/app/oracle/diag/rdbms/HOEGH/HOEGH/trace/HOEGH_dbw0_6016.trc:
ORA-01157: cannot identify/lock data file 1 - see DBWR trace file
ORA-01110: data file 1: \'/u01/app/oracle/oradata/HOEGH/system01.dbf\'
ORA-27037: unable to obtain file status
Linux Error: 2: No such file or directory
Additional information: 3
Errors in file /u01/app/oracle/diag/rdbms/HOEGH/HOEGH/trace/HOEGH_ora_6135.trc:
ORA-01157: cannot identify/lock data file 1 - see DBWR trace file
ORA-01110: data file 1: \'/u01/app/oracle/oradata/HOEGH/system01.dbf\'
ORA-1157 signalled during: ALTER DATABASE OPEN...
5.恢复数据文件
我们需要把之前的数据备份恢复到数据库当中，因此，首先我们就要解tar包，恢复之前备份的数据文件；然后，将备份的system数据文件拷贝到HOEGH数据文件目录当中。
[oracle@hoegh oradata]$ mkdir -p back
[oracle@hoegh oradata]$
[oracle@hoegh oradata]$ tar -zxvf HOEGH.tar.gz -C back/
HOEGH/
HOEGH/redo03.log
HOEGH/temp01.dbf
HOEGH/control01.ctl
HOEGH/control02.ctl
HOEGH/system01.dbf
HOEGH/sysaux01.dbf
HOEGH/users01.dbf
HOEGH/undotbs01.dbf
HOEGH/example01.dbf
HOEGH/redo02.log
HOEGH/redo01.log
[oracle@hoegh oradata]$
[oracle@hoegh oradata]$ cp back/HOEGH/system01.dbf HOEGH/