12c之后用户分为公共用户和本地用户
    1.添加公共用户

    1. # 公用用户的创建语法
    2.  create user c##lhr identified by lhr;
    3.  create user c##lhr identified by lhr default tablespace users temporary tablespace temp;
    4.  create user c##lhr identified by lhr container=all;
    6.  #给公用用户赋权
    7.  grant dba to c##lhr container=all;
    9.  #连接，可以连接到cdb，也可以连接到pdb
    10.  conn C##LHR/lhr@localhost/PDBPROD2.example.com

    2.添加本地用户

    1. create user xxt identified by lhr container=current;
    2.  grant dba to xxt container=current;
    4.  --视图查询
    5.  SELECT A.USERNAME,
    6.  A.CON_ID,
    7.  A.COMMON,
    8.  A.DEFAULT_TABLESPACE,
    9.  A.TEMPORARY_TABLESPACE
    10.  FROM CDB_users a
    11.  where a.username = 'XXT';

    3.取消12C创建用户”c##”限制

    1. alter system set common_user_prefix='' scope=spfile;
    2. 重启数据库