Computer system and data processing method

This computer system includes a plurality of nodes for forming a distributed KVS, and each of the plurality of nodes has a plurality of key ranges for which maximum data amounts have been set, each maximum data amount being an upper limit of the amount of data that can be managed. When creating a new key range, the computer system reduces the maximum data amounts for one or more existing key ranges so that the sum of the maximum data amount set for the new key range and the maximum data amounts for the one or more existing key ranges does not exceed a maximum amount determined on the basis of the memory capacities of computer devices.