A computer system comprising: an active system computer on which a business application is executed; and a standby system computer on which asynchronous replication of data is performed with the active system computer, the data being generated by executing the business application on the active system computer, wherein the active system computer comprises: a storage device for the business application to write data in; a transmission queue that queues the data not transmitted yet to the standby system computer among the data written to the storage device by the business application; receiving means that receives an advance notice for giving a failure prediction; control means that stops the execution of the business application when the receiving means receives the advance notice; and transmitting means that transmits to the standby system computer transmission start information indicating start of data transmission for failure avoidance, the data queued in the transmission queue, and transmission completion information indicating completion of the data transmission in this order when the receiving means receives the advance notice, the standby system computer comprises: a storage device; and backup means that writes the data from the active system computer to the storage device along with the asynchronous replication, and the backup means, upon a receipt of the transmission start information, writes the data received after the transmission start information to the storage device as well as generates and holds first reliability guarantee information indicating that the data received before the transmission start information is reliable data, and upon a receipt of the transmission completion information, generates and holds second reliabililty guarantee information indicating that the data received before the transmission completion information is reliable data. an active system computer on which a business application is executed; and a standby system computer on which asynchronous replication of data is performed with the active system computer, the data being generated by executing the business application on the active system computer, wherein the active system computer comprises: a storage device for the business application to write data in; a transmission queue that queues the data not transmitted yet to the standby system computer among the data written to the storage device by the business application; receiving means that receives an advance notice for giving a failure prediction; control means that stops the execution of the business application when the receiving means receives the advance notice; and transmitting means that transmits to the standby system computer transmission start information indicating start of data transmission for failure avoidance, the data queued in the transmission queue, and transmission completion information indicating completion of the data transmission in this order when the receiving means receives the advance notice, a storage device for the business application to write data in; a transmission queue that queues the data not transmitted yet to the standby system computer among the data written to the storage device by the business application; receiving means that receives an advance notice for giving a failure prediction; control means that stops the execution of the business application when the receiving means receives the advance notice; and transmitting means that transmits to the standby system computer transmission start information indicating start of data transmission for failure avoidance, the data queued in the transmission queue, and transmission completion information indicating completion of the data transmission in this order when the receiving means receives the advance notice, the standby system computer comprises: a storage device; and backup means that writes the data from the active system computer to the storage device along with the asynchronous replication, and a storage device; and backup means that writes the data from the active system computer to the storage device along with the asynchronous replication, and the backup means, upon a receipt of the transmission start information, writes the data received after the transmission start information to the storage device as well as generates and holds first reliability guarantee information indicating that the data received before the transmission start information is reliable data, and upon a receipt of the transmission completion information, generates and holds second reliabililty guarantee information indicating that the data received before the transmission completion information is reliable data.