Read-Only Tables in Oracle Database 11g

In previous Oracle releases, tables could be made to appear read-only to other users by only granting the

SELECT

object privilege to them, but the tables remained read-write for the owner. Oracle 11g allows tables to be marked as read-only using the

ALTER TABLE

command.

ALTER TABLE table_name READ ONLY;
ALTER TABLE table_name READ WRITE;

The following script creates a table, inserts a row, then sets the table to read-only.

CREATE TABLE ro_tab (
id  NUMBER
);

INSERT INTO ro_tab VALUES (1);
ALTER TABLE ro_tab READ ONLY;

Any DML statements that affect the table data and

SELECT ... FOR UPDATE

queries result in an ORA-12081 error message.

SQL> INSERT INTO ro_tab VALUES (2);
INSERT INTO ro_tab VALUES (2)
*
ERROR at line 1:
ORA-12081: update operation not allowed on table "TEST"."RO_TAB"

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

SQL> DELETE FROM ro_tab;
DELETE FROM ro_tab
*
ERROR at line 1:
ORA-12081: update operation not allowed on table "TEST"."RO_TAB"

DDL statements that affect the table data are also restricted,但是只读模式的表可以用drop命令删除。

SQL> TRUNCATE TABLE ro_tab;
TRUNCATE TABLE ro_tab
*
ERROR at line 1:
ORA-12081: update operation not allowed on table "TEST"."RO_TAB"

SQL> ALTER TABLE ro_tab ADD (description VARCHAR2(50));
ALTER TABLE ro_tab ADD (description VARCHAR2(50))
*
ERROR at line 1:
ORA-12081: update operation not allowed on table "TEST"."RO_TAB"

Operations on indexes associated with the table are unaffected by the read-only state. DML and DDL operations return to normal once the table is switched back to read-write mode.

SQL> ALTER TABLE ro_tab READ WRITE;

Table altered.

SQL> DELETE FROM ro_tab;

1 row deleted.

SQL>

The read-only status of tables is displayed in the

READ_ONLY

column of the

[DBA|ALL|USER]_TABLES

views.