The x3270 family supports file transfers via the IND$FILE utility.
Text vs. binary files
File transfers can either be in text mode or binary mode.
In text mode, translation is needed between EBCDIC on the host and the workstation's locale, and line-ending characters must be added or removed. The emulator generally handles this automatically; options are available to control the process. (Text mode is referred to as ASCII mode in many of the prompts, for historic reasons.)
In binary mode, the file is transferred without any translation.
DFT vs. CUT transfer
File transfers can use one of two protocols, DFT and CUT.
DFT mode is used with extended mode sessions. It is based on structured fields, and tends to be faster than CUT mode. CUT mode is used with the standard data stream. It is based on mappings from binary to displayable text, and tends to be slower than DFT mode.
Host record formats
Hosts generally have record-oriented files, while POSIX and Windows workstations have byte-stream files. When uploading a file from the workstation to the host, there are options to control record mapping and file allocation. In the other direction, host record boundaries are used to insert line-end sequences for text files, and are generally ignored for binary files.
Before starting a file transfer, the host session must be able to accept a command, e.g., at the VM/CMS Ready prompt, the TSO READY prompt or the ISPF Command Shell prompt. This is so the emulator can invoke the IND$FILE command.