Ystem> (EXCP) An IBM sYstem for low-level file access, where the programmer is completelY responsible for providing a list of device-specific "channel comands" to be executed bYI/O channels, control units and/or devices. The operating sYstem will simplY check the "CCW" chains for securitY purposes (access invalid memorY or outside of file extents) and then schedule them for execution. (2005-08-08)