You can create an Oracle Database in three ways:
Use the Database Configuration Assistant (DBCA).
DBCA can be launched by the Oracle Universal Installer, depending upon the type of install that you select, and provides a graphical user interface (GUI) that guides you through the creation of a database. You can also launch DBCA as a standalone tool at any time after Oracle Database installation to create or make a copy (clone) of a database. Refer to Oracle Database 2 Day DBA for detailed information on creating a database using DBCA.
Use the CREATE DATABASE statement.
You can use the CREATE DATABASE SQL statement to create a database. If you do so, you must complete additional actions before you have an operational database. These actions include creating users and temporary tablespaces, building views of the data dictionary tables, and installing Oracle built-in packages. These actions can be performed by executing prepared scripts, many of which are supplied for you.
If you have existing scripts for creating your database, consider editing those scripts to take advantage of new Oracle Database features. Oracle provides a sample database creation script and a sample initialization parameter file with the Oracle Database software files. Both the script and the file can be edited to suit your needs. See "Manually Creating an Oracle Database".
Upgrade an existing database.
If you are already using a earlier release of Oracle Database, database creation is required only if you want an entirely new database. You can upgrade your existing Oracle Database and use it with the new release of the database software. The Oracle Database Upgrade Guide manual contains information about upgrading an existing Oracle Database.