PURPOSE: To improve the overall processing efficiency of a system by sending back a condition code showing an application unable state according to the result of access decision in case an access is given to an input/output device which is under the control of a shared channel processor.

CONSTITUTION: An access deciding part 15 receives an information showing that an SIO instruction is delivered on a virtual computer from a handler 14. In this case, the part 15 decides whether the instruction is delivered from an exclusive processor and whether the access bus passes through a shared CHP5-0. If an access is given to the CHP5-0, this information is given to a condition code producing part 16. Then a condition code CC=3 showing that an input/output devide is not available with the part 16 to an access to be given to the CHP5-0 from the exclusive processor. Thus an operating system acts on the virtual computer recognizes substantially that the hardware sets the code CC=3.