The enterprise manager is usually divided into 2 sections

• Database Control

• Grid Control / Cloud Control

Database control is the most basic form of monitoring and it comes with the standard installation of Oracle as an option. During the normal installation Oracle will ask you if you either:

1. Configure Database Control, or

1. Configure Agent to Cloud control / Grid control

If a Database Control is chosen, then Oracle will configure repository for that database only

* Check the agent:

[oracle@oraprod log]$ emctl status agent
Oracle Enterprise Manager 11g Database Control Release 11.2.0.3.0 
Copyright (c) 1996, 2011 Oracle Corporation.  All rights reserved.
---------------------------------------------------------------
Agent Version     : 10.2.0.4.4
OMS Version       : 10.2.0.4.4
Protocol Version  : 10.2.0.4.4
Agent Home        : /u01/app/oracle/product/11.3.0/dbhome_2/oraprod.izola.dom_orclprod
Agent binaries    : /u01/app/oracle/product/11.3.0/dbhome_2
Agent Process ID  : 18633
Parent Process ID : 18590
Agent URL         : https://oraprod.izola.dom:3938/emd/main
Repository URL    : https://oraprod.izola.dom:1158/em/upload/
Started at        : 2017-10-06 16:33:54
Started by user   : oracle
Last Reload       : 2017-10-06 16:33:54
Last successful upload                       : (none)
Last attempted upload                        : (none)
Total Megabytes of XML files uploaded so far :     0.00
Number of XML files pending upload           :      467
Size of XML files pending upload(MB)         :    20.20
Available disk space on upload filesystem    :    25.21%
Data channel upload directory                : /u01/app/oracle/product/11.3.0/dbhome_2/oraprod.izola.dom_orclprod/sysman/recv
Collection Status                            : Disabled by Upload Manager
Last attempted heartbeat to OMS              : 2017-11-16 13:38:46
Last successful heartbeat to OMS             : unknown
---------------------------------------------------------------
Agent is Running and Ready

* Check the DB Control server:

[oracle@oraprod log]$ emctl status dbconsole
Oracle Enterprise Manager 11g Database Control Release 11.2.0.3.0 
Copyright (c) 1996, 2011 Oracle Corporation.  All rights reserved.
https://oraprod.izola.dom:1158/em/console/aboutApplication
Oracle Enterprise Manager 11g is running. 
------------------------------------------------------------------
Logs are generated in directory /u01/app/oracle/product/11.3.0/dbhome_2/oraprod.izola.dom_orclprod/sysman/log 

• Create repository

emca -config dbcontrol db -repos create

• Drop reposistory

emca -deconfig dbcontrol db -repos drop

It is important to note that, since Oracle wants to gain as much money as they can, they disabled the enterprise manager database control from 12c, HOWEVER they created Enterprise Manager express, which is at least “something” To configure the EM Express, you should just execute a simple procedure:

SQL> exec dbms_xdb_config.sethttpsport(port-number)
SQL> exec dbms_xdb_config.SetGlobalPortEnabled(TRUE)

Then you can open the following address: https://node-ip-address:EM-Express-port/em, where node-ip-address is the public IP address of the compute node hosting EM Express, and EM-Express-port is the EM Express port used by the database.

Again, this offers VERY limited functionality, like storage configuration and database settings. Global performance data like active sessions and others.