Lower case characters in IFS on Japanese language system?

Hi List:

I've been working with some folks in our Tokyo office to load some files on
the IFS ... I wrote a program that was going to recreate the necessary
directory structure and restore the IFS files from a save file.

The problem is ... some of the directories that I am creating in the IFS
(and most of the files in the save file) have lower case characters in the
name.  This appears to be causing me some problems.

When the program tries to create a directory (with lower case characters),
the system reports that the parent subdirectory cannot be found.  And when I
look at the joblog they send me (the time difference is a bear), any
characters that are lower case, show up as garbage (squares, I'm assuming
that notepad can't figure them out).

I was able to work around the problem by having them change the language to
ENU on the job that's doing the directory creation & restore ... and it
worked OK, but I would rather not have that as a requirement.

Is the PROPER way to do IFS stuff on a double byte system to use UPPER CASE
only for file names?

When they had the problem, the language was set to JPN and the CCSID was
65535.

TIA

Dave