The video consoles provided with certain models were not considered particularly user friendly, and they ignored two thirds of IBM's mainframe market, DOS and its VSE descendants.
In practice, it worked a little like present-day instant messenger programs (ICQ, QQ, AIM, Adium, iChat, etc.
DOCS was available for DOS, DOS/VS, DOS/VSE, and came packaged with third-party operating systems, such as EDOS from The Computer Software Company, later acquired by Nixdorf.
Leigh Lundin designed Fx, a pseudo-partition that relieved the user from relinquishing a working partition.
The product was also embedded in third party operating system packages, such as EDOS and vDOS.