PROBLEM TO BE SOLVED: To accelerate system maintenance by shortening time required for operation processing such as the registration, deletion or change of a user account.SOLUTION: In a server as a request source which executes processing when receiving a request for the new registration or update of an account input from a client terminal UT, a processing group corresponding to the operation classification is divided into a plurality of processing groups in accordance with the operation classification on the basis of the request, and processing belonging to each of the divided processing groups is executed in parallel by a plurality of operation target servers for each of the divided processing groups, and when the parallelization processing of the processing groups is executed, an authentication token is copied to a slave thread generated in a one-to-one relation with respect to each operation target server, and log data indicating the execution result of each slave thread are generated during the execution
