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 coded character set (CCS).
SSH Tectia Server for IBM z/OS needs more information: which transfer format to use, what coded character sets are involved, and what the file characteristics are. When SSH Tectia is used at both ends, the information can be relayed by using the Site commands of scpg3 and sftpg3, or read from environment variables. When a third-party Secure Shell client is used together with SSH Tectia Server for IBM z/OS, the information can be either encoded in the filename (advice string), read from a file transfer profile, or read from environment variables.
For more information, see SSH Tectia Server for IBM z/OS User Manual