12C配置OEM同之前的版本差别较大，没有了emctl，而是直接使用如下方法配置：
SQL*Plus: Release 12.1.0.2.0 Production on Tue Jul 19 07:19:33 2016
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Connected to:
Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production
With the Partitioning, OLAP, Advanced Analytics and Real Application Testing options
SQL> exec DBMS_XDB_CONFIG.SETHTTPPORT(8080);
PL/SQL procedure successfully completed.
SQL>
配置成功后直接访问
http://hostname:8080/em就OK了
参考文档：
To configure EM Express for a CDB:
In SQL*Plus, access a container in a CDB.
The user must have common SYSDBA administrative privilege, and you must exercise this privilege using AS SYSDBA at connect time. The container can be the root or a PDB.
See "Accessing a Container in a CDB with SQL*Plus".
Set the HTTP or HTTPS port in one of the following ways:
To set the HTTP port, run the following procedure:
exec DBMS_XDB_CONFIG.SETHTTPPORT(http_port_number);
Replace http_port_number with the appropriate HTTP port number.
To set the HTTPS port, run the following procedure:
exec DBMS_XDB_CONFIG.SETHTTPSPORT(https_port_number);
Replace https_port_number with the appropriate HTTPS port number.
Each container must use a unique port for EM Express.
Repeat steps 1 and 2 for each container that you want to manage and monitor with EM Express.
After the port is set for each container, you can access EM Express using one of the following URLs:
The URL for the HTTP port:
http://database_hostname:http_port_number/em
