To provide a data compression/decompression system that can appropriately decompress compressed data.
A first computer generates first identification information that can identify a first execution environment; and stores the first identification information on a storage device in association with compressed data of data. A second computer generates second identification information that can identify a second execution environment; and determines whether or not the first identification information, and the second identification information match. In a case that it is determined that the first identification information, and the second identification information do not match, the second computer requests a third computer that is capable of decompression of the compressed data to decompress the compressed data, the third computer decompresses the compressed data, and transmits decompressed data to the second computer, and the second computer completes the decompression of the compressed data by receiving the decompressed data from the third computer.