Abstract: A data management method in a distributed processing system having a plurality of processors connected through a common transmission line with at least one processor having at least one external device connected therewith, for sending to the common transmission line access commands issued to the external device by programs asynchronously executed in the programs as access messages; and wherein the processor having the external device connected therewith takes in any of the access messages related to the external device connected therewith from among the access messages asynchronously sent to the common transmission line by the programs, and the processor matches order of access to the external devices connected therewith among the received access messages.