For beginners and those who are unfamiliar with the components of Oracle, the Oracle DBCA has assisted uninstall procedures:
Step 1: Nuke all Oracle processes. The uninstall requires stopping all Oracle instances, listeners and daemon processes that are associated with the release:
$ORACLE_HOME/bin/emctl stop dbconsole
Step 2: Start the Database Creation Assistant (DBCA) and choose the remove database option
Step 3: Use the assisted deinstall wizard. Execute the Oracle Universal Installer (OUI)
Step 4. In the OUI Welcome window, click the “Deinstall Products” button.
Step 5. In the OUI software Inventory screen, select the Oracle home and the products that you want to remove, cross your fingers and mash the “Remove” button.