合 Oracle 11g 新特性：只读表（Read-only）

Oracle11g推出了一个新的特性，可以将table置于read only状态，处于该状态的table的不能执行DML操作和某些DDL操作。在Oracle11g之前的版本，只能将整个tablespace或者database置于read only状态。对于table的控制则只能通过权限来设定。

案例分析：

11:44:46 SCOTT@ test1 >select * from tab;

TNAME TABTYPE CLUSTERID

BONUS TABLE

CREDIT_CLUSTER CLUSTER

CREDIT_ORDERS TABLE 1

DEPT TABLE

EMP TABLE

EMP1 TABLE

11:44:56 SCOTT@ test1 >select count(*) from emp1;

COUNT(*)

----------

​ 18

Elapsed: 00:00:00.04

11:45:12 SCOTT@ test1 >alter table emp1 read only;

Table altered.

11:51:46 SCOTT@ test1 >select read_only from user_tables where table_name='EMP1';

REA

---

YES

对只读表做DML:

11:45:20 SCOTT@ test1 >insert into emp1 select * from emp where rownum=1;

insert into emp1 select * from emp where rownum=1

​ *

ERROR at line 1:

ORA-12081: update operation not allowed on table "SCOTT"."EMP1"

Elapsed: 00:00:00.04

11:45:38 SCOTT@ test1 >delete from emp1;

delete from emp1

​ *

ERROR at line 1:

ORA-12081: update operation not allowed on table "SCOTT"."EMP1"

Elapsed: 00:00:00.00

11:45:47 SCOTT@ test1 >update emp1 set sal=6000 where empno=7788;

update emp1 set sal=6000 where empno=7788

​ *

ERROR at line 1:

ORA-12081: update operation not allowed on table "SCOTT"."EMP1"

TRUNCATE TABLE:

11:46:03 SCOTT@ test1 >truncate table emp1;

truncate table emp1

​ *

ERROR at line 1:

ORA-12081: update operation not allowed on table "SCOTT"."EMP1"

Elapsed: 00:00:00.09

DROP TABLE:

11:46:45 SCOTT@ test1 >drop table emp1;

Table dropped.

Elapsed: 00:00:00.70

11:47:05 SCOTT@ test1 >show recycle;

ORIGINAL NAME RECYCLEBIN NAME OBJECT TYPE DROP TIME

EMP1 BIN$ComP5WftmQ7gUKjA+QgIyQ==$0 TABLE 2014-12-19:11:47:04

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