create user test identified by root;
grant create session,resource to root;
alter user test account unlock;
grant create view to test;
grant any sequece to test;
grant create synonym to ich;--创建别名的权限
drop user test cascade;
连接时用户民不区分大写和小写
alter system set sec_case_sensitive_logon=false scope=both;
commit;
改动用户password
alter user system identified by system; 

在用户1中建立的sequece test_seq假设想在用户2中使用(select test_seq.nextval from dual)必须如今用户2中运行select test_seq.nextval from dual;
oracle一个创建用户、创建表空间、授权、建表的完整过程
1. 用sys登录sql plus:

    usename: sys as sysdba

    password: ****

2. 查看最大连接数： select value from V$parameter where name="processes";

3. 查看当前连接数： select count (*) from V$process;

4. 把最大连接数改成300：alter system set processes=300 scope=spfile

5. 重新启动DB: shutdown immediate;

                 startup;