A system provided in an OT (Operational Technology) region, comprising: a data acquiring unit for acquiring via a communication network, from each of a plurality of sensors, provided in the OT region, measurement data generated by measuring a measurement target; a data storage unit for recording the measurement data; a priority setting unit for setting a priority to be given to each of the plurality of sensors, based on the measurement data acquired from each of the plurality of sensors, wherein the priority setting unit is configured to calculate a difference between estimation data estimated and the measurement data for each of the plurality of sensors, and set a sensor having a smaller difference to be given a lower priority than a sensor having a greater difference, wherein the priority setting unit is configured to estimate, for each of the plurality of sensors, a value of data of a target sensor from data obtained from other sensors, wherein the priority setting unit is configured to estimate a value of data of the target sensor from values of a plurality of the other sensors at locations surrounding the target sensor, by interpolating the values of the other sensors; a data selecting unit for selecting data to be deleted from among the measurement data, according to the priority for each of the plurality of sensors, wherein the data selecting unit is configured to preferentially select the measurement data acquired from the sensor with a low priority as the data to be deleted; and a data deleting unit for deleting the selected data to be deleted; and a data sending unit for sending the measurement data after deleting the selected data to be deleted to another system or apparatus provided in an IT (Information Technology) region. a data acquiring unit for acquiring via a communication network, from each of a plurality of sensors, provided in the OT region, measurement data generated by measuring a measurement target; a data storage unit for recording the measurement data; a priority setting unit for setting a priority to be given to each of the plurality of sensors, based on the measurement data acquired from each of the plurality of sensors, wherein the priority setting unit is configured to calculate a difference between estimation data estimated and the measurement data for each of the plurality of sensors, and set a sensor having a smaller difference to be given a lower priority than a sensor having a greater difference, wherein the priority setting unit is configured to estimate, for each of the plurality of sensors, a value of data of a target sensor from data obtained from other sensors, wherein the priority setting unit is configured to estimate a value of data of the target sensor from values of a plurality of the other sensors at locations surrounding the target sensor, by interpolating the values of the other sensors; a data selecting unit for selecting data to be deleted from among the measurement data, according to the priority for each of the plurality of sensors, wherein the data selecting unit is configured to preferentially select the measurement data acquired from the sensor with a low priority as the data to be deleted; and a data deleting unit for deleting the selected data to be deleted; and a data sending unit for sending the measurement data after deleting the selected data to be deleted to another system or apparatus provided in an IT (Information Technology) region.