CentOS 7
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Oracle Database 12c : Use Enterprise Manager
To access to the Enterprise Manager, it's possible to manage Database on Web GUI.
[1] After creating database, database service is running and it's possible to access to Enterprise Manager, too. Access to the URL which was displayed when database creation finished, then Login form is shown and it's possible to login with a database user.
[2] Just logined. It's possible to manage Database on here.