The PROFILE PLANGUAGE setting in effect when the OMVS TSO/E command is first issued determines the language for all OMVS command messages not from TSO/E, until you exit OMVS and return to TSO/E.

If PROFILE PLANGUAGE(JPN) is specified, and later you go to TSO/E and enter PROFILE PLANGUAGE(ENU), most TSO/E messages appear in English—including TSO/E messages about the OMVS command.

However, any OMVS command message not from TSO/E (such as the help panels invoked from <PF1> or the FSUM23-prefix messages) is displayed in Japanese. In particular, the TSO/E prompt message “OMVS - enter a TSO/E command” is still displayed in Japanese but all other messages are displayed in English while you are in TSO/E.