亲测可用，方便快捷~

1. sys/sys as sysdba登录plsql.

2. select * from user$;--获取要修改用户名的id

3. UPDATE USER$ SET NAME='DW5' WHERE USER#=162;--根据id更新用户名，仍然统一大写.

4. ALTER SYSTEM CHECKPOINT;

5. ALTER SYSTEM FLUSH SHARED_POOL;

6. ALTER USER dw5 IDENTIFIED BY dw5;--重新修改密码

用新的用户密码登录dw5/dw5登录测试~