A computer system in which a first apparatus and a second apparatus are connected via a first data communications channel, wherein the first apparatus: stores a first data in a first storage part; inquires with the second apparatus via the first data communications channel about whether the first data can be transmitted; in a case where the transmission has been approved by the second apparatus, transmits the first data to the second apparatus via the first data communications channel; and in a case where the transmission has not been approved by the second apparatus, receives a second data from the second apparatus via the first data communications channel, and outputs the first data and the second data to a storage medium, wherein the second apparatus: stores the second data in a second storage part; upon receiving an inquiry from the first apparatus via the first data communications channel about whether the first data can be transmitted, determines whether the first data can be transmitted from the first apparatus on the basis of a threshold related to the volume of communications of a second data communications channel during a first time period that includes the current time point, the threshold is configured as a condition pertaining to the second data communications channel that can be used by the second apparatus, the determination, based on the threshold and the post-transmission communications volume of the second data communications channel during the first time period, is performed on the supposition that the first data and the second data are transmitted over the second data communications channel; in the case where the post-transmission communications volume is larger than the threshold, determines not to approve the transmission of the first data from the first apparatus; upon having determined to approve the transmission of the first data from the first apparatus, receives the first data from the first apparatus via the first data communications channel, and transmits the first data and the second data to a server via the second data communications channel; and upon having determined not to approve the transmission of the first data from the first apparatus, transmits the second data to the first apparatus via the first data communications channel. stores a first data in a first storage part; inquires with the second apparatus via the first data communications channel about whether the first data can be transmitted; in a case where the transmission has been approved by the second apparatus, transmits the first data to the second apparatus via the first data communications channel; and in a case where the transmission has not been approved by the second apparatus, receives a second data from the second apparatus via the first data communications channel, and outputs the first data and the second data to a storage medium, stores the second data in a second storage part; upon receiving an inquiry from the first apparatus via the first data communications channel about whether the first data can be transmitted, determines whether the first data can be transmitted from the first apparatus on the basis of a threshold related to the volume of communications of a second data communications channel during a first time period that includes the current time point, the threshold is configured as a condition pertaining to the second data communications channel that can be used by the second apparatus, the determination, based on the threshold and the post-transmission communications volume of the second data communications channel during the first time period, is performed on the supposition that the first data and the second data are transmitted over the second data communications channel; in the case where the post-transmission communications volume is larger than the threshold, determines not to approve the transmission of the first data from the first apparatus; upon having determined to approve the transmission of the first data from the first apparatus, receives the first data from the first apparatus via the first data communications channel, and transmits the first data and the second data to a server via the second data communications channel; and upon having determined not to approve the transmission of the first data from the first apparatus, transmits the second data to the first apparatus via the first data communications channel.