You can use Database Configuration Assistant (DBCA) to change the configuration of an existing database. For example, you can make configuration changes such as:
Add database options that were not previously configured (for example, Oracle Label Security or Oracle OLAP)
Change default security settings
Change the server mode from dedicated to shared, or the reverse
To change the configuration of a database using DBCA:
Start DBCA as described in "Starting DBCA".
In the Database Operation window, select Configure Database Options and click Next.
Follow the instructions in the DBCA guided workflow.