在數據庫中創建表空間 tyger2 在linux系統文件中刪除了數據文件 tyger2_01.dbf 啟動數據庫報錯，
重新創建名字為tyger2_01.dbf 文件，數據庫正常啟動，但是數據文件中的數據一定不在了。
啟動 Oracle 數據庫實例：OPEN
數據庫操作正常意味著實例已啟動、數據庫已裝載且已打開。通過執行正常數據庫操作，任何有效用戶都可連接到數據庫，而且可執行典型數據訪問操作。
打開數據庫過程包括執行以下任務：
打開聯機數據文件
打開聯機重做日志文件
如果嘗試打開數據庫時任一數據文件或聯機重做日志文件不存在，則 Oracle 服務器返回錯誤。
在最後這個階段，Oracle 服務器會驗證是否可以打開所有的數據文件和聯機重做日志文件，還會檢查數據庫的一致性。如有必要，系統監視器 (SMON) 後台進程將啟動實例恢復。
可以在受限模式下啟動數據庫實例，使得只讓有管理權限的用戶使用該實例。要在受限模式下啟動實例，請在“Advanced Startup Options（高級啟動選項）”頁上選擇“Restrict access to database（限制對數據庫進行訪問）”選項。
接著實驗：
http://blog.csdn.net/wanghui5767260/article/details/20293807
【精】ORA-01157: cannot identify/lock data file 6 - see DBWR trace file ORA-01110: 解決方法
[oracle@tyger ~]$ sqlplus / as sysdba
SQL*Plus: Release 10.2.0.1.0 - Production on Sun Mar 2 17:21:38 2014
Copyright (c) 1982, 2005, Oracle. All rights reserved.
Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production
With the Partitioning, OLAP and Data Mining options
SYS@ORCL>create tablespace tyger2 datafile '/u01/app/oracle/oradata/ORCL/tyger2_01.dbf' size 5m;
Tablespace created.
SYS@ORCL>create user tygeru2 identified by tygeru2 account unlock default tablespace tyger2;
create user tygeru2 identified by tygeru2 account unlock default tablespace tyger2
*
ERROR at line 1:
ORA-01920: user name 'TYGERU2' conflicts with another user or role name
SYS@ORCL>alter user tygeru2 default tablespace tyger2;
User altered.
SYS@ORCL>conn tygeru2/tygeru2
Connected.
TYGERU2@ORCL>select username,default_tablespace from user_users;
USERNAME DEFAULT_TABLESPACE
------------------------------ ------------------------------
TYGERU2 TYGER2
TYGERU2@ORCL>create table u2_t1 as select * from scott.emp;
Table created.
TYGERU2@ORCL>
TYGERU2@ORCL>commit;
Commit complete.
TYGERU2@ORCL>select count(*) from u2_t1;
COUNT(*)
----------
14
TYGERU2@ORCL>!
[oracle@tyger ~]$ cd $ORACLE_BASE/oradata/ORCL
[oracle@tyger ORCL]$ ll
total 1068456
-rw-r----- 1 oracle oinstall 7061504 Mar 2 17:25 control01.ctl
-rw-r----- 1 oracle oinstall 7061504 Mar 2 17:25 control02.ctl
-rw-r----- 1 oracle oinstall 7061504 Mar 2 17:25 control03.ctl
-rw-r----- 1 oracle oinstall 104865792 Mar 2 17:19 example01.dbf
-rw-r----- 1 oracle oinstall 52429312 Mar 2 17:19 redo01.log
-rw-r----- 1 oracle oinstall 52429312 Mar 2 17:19 redo02.log
-rw-r----- 1 oracle oinstall 52429312 Mar 2 17:25 redo03.log
-rw-r----- 1 oracle oinstall 251666432 Mar 2 17:24 sysaux01.dbf
-rw-r----- 1 oracle oinstall 503324672 Mar 2 17:24 system01.dbf
-rw-r----- 1 oracle oinstall 20979712 Mar 1 08:42 temp01.dbf
-rw-r----- 1 oracle oinstall 5251072 Mar 2 17:25 tyger2_01.dbf
-rw-r----- 1 oracle oinstall 26222592 Mar 2 17:24 undotbs01.dbf
-rw-r----- 1 oracle oinstall 5251072 Mar 2 17:19 users01.dbf
[oracle@tyger ORCL]$ mv tyger2_01.dbf tyger2_01.dbf.bak
[oracle@tyger ORCL]$ ll
total 1068456
-rw-r----- 1 oracle oinstall 7061504 Mar 2 17:25 control01.ctl
-rw-r----- 1 oracle oinstall 7061504 Mar 2 17:25 control02.ctl
-rw-r----- 1 oracle oinstall 7061504 Mar 2 17:25 control03.ctl
-rw-r----- 1 oracle oinstall 104865792 Mar 2 17:19 example01.dbf
-rw-r----- 1 oracle oinstall 52429312 Mar 2 17:19 redo01.log
-rw-r----- 1 oracle oinstall 52429312 Mar 2 17:19 redo02.log
-rw-r----- 1 oracle oinstall 52429312 Mar 2 17:25 redo03.log
-rw-r----- 1 oracle oinstall 251666432 Mar 2 17:24 sysaux01.dbf
-rw-r----- 1 oracle oinstall 503324672 Mar 2 17:24 system01.dbf
-rw-r----- 1 oracle oinstall 20979712 Mar 1 08:42 temp01.dbf
-rw-r----- 1 oracle oinstall 5251072 Mar 2 17:25 tyger2_01.dbf.bak
-rw-r----- 1 oracle oinstall 26222592 Mar 2 17:24 undotbs01.dbf
-rw-r----- 1 oracle oinstall 5251072 Mar 2 17:19 users01.dbf
[oracle@tyger ORCL]$ exit
exit
TYGERU2@ORCL>conn / as sysdba
Connected.
SYS@ORCL>shutdown abort
ORACLE instance shut down.
SYS@ORCL>startup
ORACLE instance started.
Total System Global Area 285212672 bytes
Fixed Size 1218992 bytes
Variable Size 138413648 bytes
Database Buffers 142606336 bytes
Redo Buffers 2973696 bytes
Database mounted.
ORA-01157: cannot identify/lock data file 6 - see DBWR trace file
ORA-01110: data file 6: '/u01/app/oracle/oradata/ORCL/tyger2_01.dbf'
SYS@ORCL>alter database datafile 6 offline drop;
Database altered.
SYS@ORCL>alter database open;
Database altered.
SYS@ORCL>conn tygeru2/tygeru2
Connected.
TYGERU2@ORCL>select count(*) from u2_t1;
select count(*) from u2_t1
*
ERROR at line 1:
ORA-00376: file 6 cannot be read at this time
ORA-01110: data file 6: '/u01/app/oracle/oradata/ORCL/tyger2_01.dbf'
結論：
數據庫可以啟動了，但是數據問價已經在數據庫中drop了 所以數據都不存在了
