To prevent the waste of a memory and to keep the updating of a simultaneously executable task number to an irreducible minimum by deciding the simultaneously executable task number based on operation statistical information.

This system is constituted of a terminal equipment 1, a terminal input means 2, a transaction execution control means 3, a transaction operation statistical information control means 4, a transaction execution class operation statistical information management chart 5 for respective time bands, a timer acquisition device 6, a change means 7 for the number of transaction processing tasks, a timer informing device 8 and an application program 9. Based on the operation statistical information for the execution class of transactions for the respective time bands, the number of transaction execution tasks is automatically decided, a large number of transaction execution tasks are allocated to the transaction with a large number of processing items and a small number of transaction execution tasks are allocated to the transaction with a small number of executions depending on the time band.