A database management system has a plurality of database servers and data can be transferred between them by partitioning a data area into small areas and altering allocation of the small areas to the database servers. After altering the configuration, there occurs degradation in processing speed that accompanies re-creation of the index. If this problem is solved by using conventional techniques, noticeable degradation in processing speed will occur to a specific query at the time of a steady state operation. Accordingly, an index created for each of the small areas and an index to all of the small areas are allocated to the database server and used in combination.