Fault tolerant system and controller, access control method, and control program used in the fault tolerant system

A controller used in a fault tolerant system including a plurality of systems constituted by the same processor section and input/output section, the controller comprising:

• tag assignation means for assigning tag information to access data that are transmitted from the processor section to the input/output section, the tag information including:
• identifying information of the access source and destination;
• and synchronization information indicating whether the access data is synchronous access data that has been issued when the processor section is in a lock-step synchronous state;
• buffer means for separately retaining the access data of the own system and other system that are transmitted from the processor section;
• synchronization determination means for determining whether the access data is synchronous access data based on the tag information assigned to the access data in the buffer means;
• and
• processing means for outputting the access data from one of the plurality of systems to the input/output section and discarding the access data from other systems in the case where the access data is synchronous access data.

An access control method used in a fault tolerant system including a plurality of systems constituted by the same processor section and input/output section, the access control method comprising the steps of:

• assigning tag information to access data that are transmitted from the processor section to the input/output section, the tag information including:
• identifying information of the access source and destination;
• and synchronization information indicating whether the access data is synchronous access data that has been issued when the processor section is in a lock-step synchronous state;
• separately retaining the access data of the own system and other system that are transmitted from the processor section;
• determining whether the access data is synchronous access data based on the tag information assigned to the access data in the buffer means;
• and
• outputting the access data from one of the plurality of systems to the input/output section and discarding the access data from other systems in the case where the access data is synchronous access data.

A control program used in a fault tolerant system including a plurality of systems constituted by the same processor section and input/output section, the control program enabling a computer to execute an access control method comprising the steps of:

• assigning tag information to access data that are transmitted from the processor section to the input/output section, the tag information including:
• identifying information of the access source and destination;
• and synchronization information indicating whether the access data is synchronous access data that has been issued when the processor section is in a lock-step synchronous state;
• separately retaining the access data of the own system and other system that are transmitted from the processor section;
• determining whether the access data is synchronous access data based on the tag information assigned to the access data in the buffer means;
• and
• outputting the access data from one of the plurality of systems to the input/output section and discarding the access data from other systems in the case where the access data is synchronous access data.