Automatic Transfer of Sense Data to Channel
Original Publication Date: 1982-Aug-01
Included in the Prior Art Database: 2005-Feb-10
On the IBM System/370 channel, errors in I/O operations are handled as follows: When the device or control unit detects an error during an I/O operation, it ends the operation with unit check status and preserves detailed information about the error in its sense register. When the I/O Supervisor perceives the unit check status, it issues the sense command, as a new I/O operation, to the device to obtain the contents of the sense register. This information is then made available to the access method programs. Because the sense operation is, itself, an I/O operation, and is performed within the processing of another I/O operation, the software to perform this operation is complex. Furthermore, the sense operation, being an I/O operation, is subject to its own I/O errors.