PURPOSE: To improve the reliability of a system by bringing an abnormality which has been detected by a transfer device having no service processor (SVP) interface, to logout to an SVP through a processor from said transfer device.

CONSTITUTION: When a transfer device (CH) 2 has detected an abnormality of itself and an input/output device I/O 3 being under its control, a bus use request word is sent out in order to report said abnormality as a channel status word CSW, but in that case, abnormality cause information which cannot be represented by the CSW is loaded on an undefined part of the bus request work, and sent out by adding newly a log request flag to a flat part, and setting it. A CPU 1 analyzes this bus use request word, knows that it is a command from the CH 2, and a log request exists, holds it, and thereafter, executes an interruption to an SVP 5, and executes the log request. The SVP 5 receives this log request and inputs log information which has been held. When a bus use permission is received, the CSW is written in a prescribed area of a main storage device (MEM) 4.