The current Secure Shell protocol and current clients do not transfer any information about the files to be transferred, only the file contents as a byte stream. This is sufficient for Unix-type files if the sender and receiver use the same CCS.
SSH Tectia Server for IBM z/OS needs more information: which transfer format to use, what code sets are involved, and what the file characteristics are. Some of this information may be transported in the protocol in the future versions of SSH Tectia Client. In SSH Tectia Server for IBM z/OS, the information is either encoded in the filename (Advice String), read from a file transfer profile, or in case of file transfer client from environment variables.