The MSGCASE system initialization parameter specifies how you want the message domains to display mixed case messages.
Mixed case output is not displayed correctly on Katakana display terminals and printers. Uppercase English characters appear correctly as uppercase English characters, but lowercase appears as Katakana symbols. If you have any Katakana terminals connected to your CICS region, specify MSGCASE=UPPER.
If you want to use uppercase English for your CICS-WebSphere MQ components, you must set MSGCASE=UPPER, and ensure that ASSIGN NATLANGINUSE returns E (US English).