Installer/Installation Dialogs Language
Oracle Universal Installer (OUI) runs in the language of the operating system. OUI uses the language that Java detects, the system locale value, and sets that to the default language. The Installer dialogs will be displayed in this language if available. If specific Installer dialogs are not translated in the language of the operating system, those dialogs will be shown in English.
Product Language Selections
If multiple languages are defined for the products installed, the Universal Installer allows language selection via the Custom install type only. The languages selections are for the top level component being installed. A top level component is the product selected on the Products Selection dialog, a single one per installation session. If any sub-components (lower level) do not have files defined for the language the user selects, English only will be installed. The English files are always installed for all components, regardless of user selection or operating system language.
If a component is already installed, but with a different language set, that component will be reinstalled.
At install time, OUI looks at the language list of each file/filegroup to determine which need to be copied.