Oracle Enterprise Manager Grid Control Advanced Installation and Configuration Guide 11g has the following section:
How can you change the language used in Enterprise Manager Grid Console?
By default, the Enterprise Manager Grid Control Installation Wizard
installs Enterprise Manager Grid Control console with English
language. If you want to view them in another language, then select
the required languages in the Select Languages screen of the
Note: The language you select here changes the language used in the
Enterprise Manager Grid Control console screens only; it does NOT
change the language used in the installation wizard screens. The
language of the installation wizard screens is based on the operating
When you select additional languages to install, the installation
wizard also installs fonts required to display the languages.
For some components, languages are installed only if you select them
during installation. In this case, if you access the application in a
language that is not available, it reverts to the locale language.
For other components, available languages are installed regardless of
what you select during installation. In this case, however, fonts are
installed only for the languages that are explicitly selected. When
you access the application, it uses text in your language because the
language was installed. However, if you do not have the appropriate
fonts to render the text, the text appears as square boxes. This
usually applies to the Chinese, Japanese, and Korean languages.