A commit controlling scheme for a transaction processing in a system utilizing the check point/roll back scheme, which is capable of guaranteeing the reliability of data of the transaction processing even when the transaction processing and the check point/roll back scheme are employed simultaneously, is described. An issuance of an external output for notifying to a user that a transaction has been committed is delayed until after a new check point for the transaction processing process is generated by the fault recovery mechanism at a timing later than a commit of the transaction by the transaction processing process. This can be realized by delaying an issuance of a transaction commit notice from the transaction processing process, or by intercepting a transaction commit notice sent from the transaction processing process, or else by delaying an issuance of the external output by the client process after receiving a transaction commit notice from the transaction processing process.