1.将users表空间改成只读，分析只读表空间的特点
SQL> alter tablespace users read only;
Tablespace altered.
SQL> select checkpoint_change#,file# from v$datafile;
CHECKPOINT_CHANGE# FILE#
------------------ ----------
3102641 1
3102641 2
3102641 3
3102607 4
3102641 5
3102641 6
只读表空间，自改为自读那一刻起
ckpt就不再维护该表空间所有数据文件的文件头检查点信息了
也不再控制文件中这些数据文件的检查点的信息
这些只读文件的检查点信息被永恒的固定到了改为自读的那一刻
除非，将该表空间重新改为read write，否则，这些文件的检查点信息永远不变
2.备份只读表空间
对于只读表空间的备份
不需要像普通表空间那样，在执行热备的时候，要begin..end backup
可以在数据库正常开启或关闭的时候直接进行复制
SQL> select name from v$datafile;
NAME
----------------------------------------------------------
/u01/app/oracle/oradata/orcl/system01.dbf
/u01/app/oracle/oradata/orcl/sysaux01.dbf
/u01/app/oracle/oradata/orcl/undotbs01.dbf
/u01/app/oracle/oradata/orcl/users01.dbf
/u01/app/oracle/oradata/orcl/example01.dbf
/u01/app/oracle/oradata/orcl/idx_tbs01.dbf
6 rows selected.
SQL> !cp /u01/app/oracle/oradata/orcl/users01.dbf /u03
3.只读表空间的恢复
模拟故障
SQL> !rm -rf /u01/app/oracle/oradata/orcl/users01.dbf
SQL> conn scott/tiger
Connected.
SQL> select * from emp;
select * from emp
*
ERROR at line 1:
ORA-01116: error in opening database file 4
ORA-01110: data file 4: '/u01/app/oracle/oradata/orcl/users01.dbf'
ORA-27041: unable to open file
Linux Error: 2: No such file or directory
Additional information: 3
恢复
offline-复制-online，不需要进行recover
SQL> conn / as sysdba
Connected.
SQL> alter database datafile 4 offline;
Database altered.
SQL> !cp /u03/users01.dbf /u01/app/oracle/oradata/orcl/users01.dbf
SQL> alter database datafile 4 online;
Database altered.
SQL> conn scott/tiger
Connected.
SQL> select * from emp;
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7369 SMITH CLERK 7902 17-DEC-80 800 20
7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30
7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30
7566 JONES MANAGER 7839 02-APR-81 2975 20
7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7839 KING PRESIDENT 17-NOV-81 5000 10
7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
7876 ADAMS CLERK 7788 23-MAY-87 1100 20
7900 JAMES CLERK 7698 03-DEC-81 950 30
7902 FORD ANALYST 7566 03-DEC-81 3000 20
7934 MILLER CLERK 7782 23-JAN-82 1300 10