the db buffer within the dbms 103 otherwise if the query retrieved from the tr queue 310 has not been copied to the tr management unit 320 in the secondary site the tr duplication and execution unit 302 determines whether copying the query to the secondary site is required if the query is not a commit the tr duplication and execution unit 302 immediately executes the query without copying it otherwise if the query is a commit the tr duplication and execution unit 302 executes a synchronous sync copy to the tr management unit 320 in the secondary site by the sync copy not only the query but also all uncopied data of queries of transactions stored in the tr queue 310 are copied simultaneously to the tr management unit 320 then the tr duplication and execution unit 302 executes the query to be executed thus because the tr duplication and execution unit 302 before executing a commit always copies the data of the queues constituting the transaction relevant to the commit to the tr management unit 320 in the secondary site it is ensured that no part of the transaction data is missing the tr management unit 320 in the secondary site is comprised of a tr receive and execution unit 321 a recovery unit 340 a tr queue 322 and a recovery table 341 the tr receive and execution unit 321 receives a transaction copied from.