 Should the DEB include additional extents, the channel program may be updated by the programmer to refer to the next extent and the EXCP may be reissued, or the end of extent exit appendage, if provided, may update the channel program to the next extent and the operation may be re-driven without first going through the EXCP processor.EXCP is sometimes confused with a direct access storage device access method, but it is not for direct access storage devices exclusively; rather, it is a general purpose low-level device access interface which supports any "legacy" device type and any "legacy" dataset organization.For accessing "all" device types and "all" dataset organizations, the more general Start Input/Output interface (STARTIO) is available in MVS/370 and subsequent instances of the OS although it is not an officially supported interface.