ORACLE 12C开启EM EXPRESS过程
1 首先启动监听和关闭ORACLE/LINUX防火墙（这一步略过）
lsnrctl start
2 然后查看http和https端口
select dbms_xdb_config.gethttpsport() from dual;
select dbms_xdb_config.gethttpport() from dual;
3 设置em端口
exec dbms_xdb_config.setHTTPSPort(8089);
exec dbms_xdb_config.setHTTPPort(8090);