Enable EM Express
After installing 12c database, you may want to enable dbconsole just like 10g and 11g, but in fact, there's no emctl command to operate with. This is because 12c or later uses EM Express version instead of dbconsole. It's enabled by default.
Port Number
Before accessing EM Database Express 12c, you have to make sure which port is used.
SQL> select dbms_xdb_config.getHttpsPort() port_number from dual;
PORT_NUMBER
-----------
5500
As you can see, Port 5500 is set for EM Express 12c. Actually, 5500 is the default value. If the result is empty or undesired, you can use the following function to change it.
SQL> exec dbms_xdb_config.sethttpsport(5500);
PL/SQL procedure successfully completed.
To check the result, we can retrieve current EM port like this:
SQL> select dbms_xdb_config.gethttpsport "EM Port" from dual;
EM Port
----------
5500
Now we can connect EM. Let's see the format of connection URL:
https://<IP Address>:<Port Number>/em/logon
Where IP Address can be the hostname of your database server, as long as it can be resolved by DNS. For a RAC system, it can be SCAN IP, VIP or Public IP. But SCAN is better.
Access Account
As a DBA, you can logon the GUI as sys or system. But for others like system operators, you can give them a specific user account with basic privileges to logon EM Express.
In the followings, I create a user named embasic dedicated for accessing EM express, then I grant some proper privileges to it.
SQL> create user embasic identified by <password>;
User created.
SQL> grant connect to embasic;
Grant succeeded.
SQL> grant EM_EXPRESS_BASIC to embasic;
Grant succeeded.
Where EM_EXPRESS_BASIC is a role which enables users to monitor performance in EM Express.
Express version of enterprise manager is bundled with database software and very handy to use but very limited in functions, compared with grid control or cloud control 12c which are separate products in Oracle and should be running on standalone machines.
To revert the setting, you can turn EM Express off.