File transfer is as essential as terminal emulation. Most have a proprietary file transfer that is generally a great deal speedier than IBM's. On the other hand, that requires more memory on the PC side. The gateway should also allow users to transfer files in background mode. With background file transfer, a user can set up a file transfer and switch to an interactive terminal session while the transfer takes place.
Most gateways allow users to have multiple, simultaneous sessions on the mainframe.
Some gateways limit this to a specific number, say two terminal sessions and one printer session per user. Others allow one user to hog every session the gateway has available. It is very useful if the software supports windowing, so the various sessions can be overlaid on a single screen. The PC keyboard must be remapped to emulate the 3270 terminal keyboard. The PF keys must be added to the PC keyboard.