oracle 忘记用户名和密码，修改方法
cmd
sqlplus /nolog
connect / as sysdba
创建用户以及设置密码
create user username identified by password;
如：
create user user1 identified by 123456;
修改用户：
alter user user1 identified by 234567;
撤销用户user1：
drop user user1;
为user1 授权：
grant connect ,resource to user1;
撤销对user1赋予的权限：
revoke connect,resource from user;