Transaction processing system having service level control capabilities

There is provided a transaction processing system for providing plural services according to service level contracts, the system comprising: an SLA database for storing contract conditions defined for each of the services provided; request queues for storing processing requests sent from clients for the services provided while putting the respective services into a particular order; queuing condition detection module for obtaining waiting conditions of the processing requests stored in the request queues; and a scheduler for deciding priorities to the processing requests input from the client to the transaction processing system by referring to the contract conditions and the waiting conditions of the processing requests.