建立test使用者：
[email protected]>create user test identified by test;                                                                                                                                  

User created.

查詢test資訊：

[email protected]>select user#,name,password from user$ where name ='TEST';                                                                                                             

               USER# NAME                           PASSWORD
-------------------- ------------------------------ ------------------------------
                 474 TEST                           7A0F2B316C212D67

修改使用者名稱：

[email protected]>update  user$ set name='TEST_BAK' where user#=474;                                                                                                                    

1 row updated.

Commit complete.

[email protected]>select user#,name,password from user$ where name ='TEST';                                                                                                             

no rows selected

[email protected]>select user#,name,password from user$ where name ='TEST_BAK';                                                                                                         

               USER# NAME                           PASSWORD
-------------------- ------------------------------ ------------------------------
                 474 TEST_BAK                       7A0F2B316C212D67

建立相同使用者：

[email protected]>create user test identified by test;                                                                                                                                  
create user test identified by test
            *
ERROR at line 1:
ORA-01920: user name 'TEST' conflicts with another user or role name

強制oracle將資料寫入磁碟：
[email protected]>alter system checkpoint;                                                                                                                                              

System altered.

清空記憶體，使資料庫讀取磁碟資料：

[email protected]>alter system flush shared_pool;                                                                                                                                       

System altered.

再次建立test使用者：

[email protected]>create user test identified by test;                                                                                                                                  

User created.
成功。