A computer-readable, non-transitory medium stores a program that manages compressed file groups on a plurality of slave servers. The file groups include compressed files that are to be searched and have character strings. Each of the compressed file groups is expanded, using a Huffman tree that was used for compressing the compressed file group. A common compression parameter is generated based on appearance frequency, by summing, for each character, the appearance frequency in each of the compressed file groups. The expanded files are recompressed using the common Huffman tree such that sums of the access frequencies of the compressed files that are origins of the recompressed files are substantially equivalent among various slave servers. New archives including the re-compressed files are transmitted to the respective slave servers.