在不知道用户密码的时候，怎么样跳转到另外一个用户执行操作后并不影响该用户?

需要Alter user权限或DBA权限:

sql> select password from dba_users where username='SCOTT';

PASSWORD

-----------------------------

F894844C34402B67

sql> alter user scott identified by lion;

User altered.

sql> connect scott/lion

Connected.

REM Do whatever you like...

sql> connect system/manager

Connected.

sql> alter user scott identified by values 'F894844C34402B67';

User altered.

sql> connect scott/tiger

Connected