Method of changing system configuration in shared-nothing database management system
A shared-nothing database management system employs a method of adding and removing a database server without significantly affecting the processing performance for accessing a table from a user or an application. A scheduler module creates a schedule which separately handles the addition of a CPU resource and the addition of a storage I/O resource, and a server is added in accordance with the created schedule. A common disk is used to remove a disk at an arbitrary timing. Further, a data region is previously subdivided on the common disk to eliminate a movement of data associated with the addition of a server.
1. A system configuration changing method in a shared-nothing database management system which includes a plurality of CPU resources, a storage, and a network for connecting said CPU resources and said storage, wherein each of said plurality of CPU resources runs a database search program stored in a computer readable medium being executable by a processor so that each functions as a backend module for processing data, said method comprising the steps of:
allocating physically independent data regions of the storaae to respective CPU resources by a mapping module;
adding to said shared-nothing database management system a backend module exclusively for sorting and merging data without accessing a table in a database, wherein the added backend module sorts and merges data by receiving the data from other backend modules that have read the data from said storage;
determining whether or not a storage I/O resource is to be added to said backend module exclusively for sorting and merging data;
changing said backend module exclusively for sorting and merging data to an ordinary backend module for accessing a table in a database in response to a determination that the storage I/O resource is to be added; and
relocating data after a load on a group of active backend modules is reduced to a system-defined value or a user-defined value in response to the determination that the storage I/O resource is to be added.