1. A transaction processing method, comprising the steps of: executing a plurality of transactions that carry out update processing with respect to one file read out onto a buffer region; and writing said one file into a stable memory device at a time of commit of one transaction among the plurality of transactions, said one file containing a content of committed updates made by said one transaction and a content of non-committed updates made by other non-committed transactions, and information for cancelling the non-committed updates.