SQL> show user

User is "SYS"

SQL> set transaction read only;

Transaction set

SQL> insert into t_table values(3);

1 row inserted

SQL> commit;

Commit complete

---sys用户 set transaction read only不生效

SQL> select * from t_table;

A

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1

2

3

SQL>

SQL>

SQL> ---换另一个普通用户

SQL> conn

Connected to Oracle Database 11g Enterprise Edition Release 11.2.0.1.0

Connected as

SQL> create table t_transaction(a int);

Table created

SQL> set transaction read only;

Transaction set

SQL> insert into t_table values(3);

insert into t_table values(3)

ORA-00942: table or view does not exist

---仅在非sys用户 set transaction read only才生效

SQL> insert into t_transaction values(3);

insert into t_transaction values(3)

ORA-01456: may not perform. insert/delete/update operation inside a READ ONLY transaction

SQL> delete from t_transaction;

delete from t_transaction

ORA-01456: may not perform. insert/delete/update operation inside a READ ONLY transaction

SQL> update   t_transaction set a=3;

update   t_transaction set a=3

ORA-01456: may not perform. insert/delete/update operation inside a READ ONLY transaction

--truncate为ddl语句不受set transaction read only影响

SQL> truncate table t_transaction;

Table truncated

SQL> show user

User is "tbl_bck"

---也可以用dbms_transaction包实现上述的只读事务功能

SQL> exec dbms_transaction.read_only;

PL/SQL procedure successfully completed

SQL> insert into t_transaction values(8);

insert into t_transaction values(8)

ORA-01456: may not perform. insert/delete/update operation inside a READ ONLY transaction

--dbms_transaction.read_only|write只能用于事务开始而非结束

SQL> exec dbms_transaction.read_write;

begin dbms_transaction.read_write; end;

ORA-01453: SET TRANSACTION must be first statement of transaction

ORA-06512: at "SYS.DBMS_TRANSACTION", line 60

ORA-06512: at line 2

SQL>

SQL>

SQL> set transaction read write;

set transaction read write

ORA-01453: SET TRANSACTION must be first statement of transaction

---必须用dbms_transaction.commit或rollback方可结束一个只读事务

SQL> exec dbms_transaction.commit;

PL/SQL procedure successfully completed

SQL> insert into t_transaction values(8);

1 row inserted

SQL> commit;

Commit complete

---dbms_transaction包另一个功能可以直接内嵌于存储过程中,进行针对性的控制

SQL> create or replace procedure proc_transaction

2  as

3  v_a pls_integer;

4  begin

5  dbms_transaction.read_only;

6  select count(1) into v_a from dual;

7  dbms_transaction.commit;

8  insert into t_transaction values(9);

9  commit;

10  end;

11  /

Procedure created

SQL> exec proc_transaction;

PL/SQL procedure successfully completed

SQL> select * from t_transaction;

A

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8

9