Handling of invalid byte streams
Many encodings place restrictions on which byte sequences are acceptable. For example, Big5 requires that the first byte is from A1h to FEh. The second byte must be from 40h to 7Eh or A1h to FEh. If an inbound byte stream is not valid for the encoding in use, then the message is transitioned to the error database with error state 416: Inbound encoding conversion error.
These messages are unintelligible and cannot be converted to Unicode, so the raw byte stream is stored in the error database. Outbound messages always consist of valid byte streams. Byte stream validity for an encoding is a separate issue from the ability of an encoding to represent all the Unicode characters in a message.