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。
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]$
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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...
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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