Multibyte code pages are not supported completely

What causes this issue?

The usage of non-Unicode code pages with a variable byte length
(multibyte code pages) is not supported completely.

System Response

How to fix this error?

See SAP Note 2499691.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.