Oracle 11g 新特性：只读表（Read-only）

在Oracle 11g前的版本中，若想对表设置为只读，可以通过赋予SELECT对象权限给这些用户，但表的拥有者还是读写的。而Oracle 11g 允许表标记为只读（read-only)通过ALTER  TABLE 命令。
可以通过下面命令对表读写权限进行设置：
  ALTER  TABLE  table_name READ ONLY;
  ALTER  TABLE  table_name READ WRITE;
简单示例如下：
CREATE  TABLE ro_test (
    id  number
 );
INSERT  INTO  ro_test  VALUES (1);
ALTER  TABLE  ro_test  READ ONLY;
 
任何影响表数据的DML语句和SELECT...FOR UPDATE查询语句都返回ORA-12081错误信息
SQL> INSERT INTO ro_test  VALUES (2);
INSERT INTO ro_test  VALUES (2)
            *
ERROR at line 1:
ORA-12081: update operation not allowed on table "TEST"."RO_TEST"

SQL> UPDATE ro_test  SET id = 2;
UPDATE ro_test  SET id = 2
      *
ERROR at line 1:
ORA-12081: update operation not allowed on table "TEST"."RO_TEST"

SQL> DELETE FROM ro_test;
DELETE FROM ro_test
            *
ERROR at line 1:
ORA-12081: update operation not allowed on table "TEST"."RO_TEST"
影响表数据的DDL语句也受限制
SQL> TRUNCATE TABLE ro_test;
TRUNCATE TABLE ro_test
              *
ERROR at line 1:
ORA-12081: update operation not allowed on table "TEST"."RO_TEST"

SQL> ALTER TABLE ro_test ADD (description VARCHAR2(50));
ALTER TABLE ro_test ADD (description VARCHAR2(50))
*
ERROR at line 1:
ORA-12081: update operation not allowed on table "TEST"."RO_TEST"
表是只读表但在与之相关的索引上操作不受影响。当表切换回读写模式时DML和DDL操作恢复正常。
SQL> ALTER TABLE ro_test READ WRITE;
Table altered.
SQL> DELETE FROM ro_test;
1 row deleted.
SQL>