Channel to channel adapter

In IBM mainframe technology, a channel-to-channel adapter (CTCA) is a device which connects two channels on (usually) two separate computer systems.

The adapter allows one computer system to be treated as an input/output device by another. It is used "to link the processing units in a loosely coupled multiprocessing system."

Virtual channel-to-channel adapters are often used to communicate between two virtual machines in the z/VM operating system.