An OS-level backup makes a copy, on alternate media, of the entire set of disk resources that the database was using at a single point in time. In general, you cannot make a consistent OS-level backup while any of the disk resources of the database is changing. In IQ multiplex, this means that you must stop the write server to keep it from modifying any of its disk resources during the OS-level backup. Query servers, however, may continue to run since they cannot modify the shared IQ Main disk resources, and their Catalog and Temporary Stores are private and need not be backed up. However, if the query server has an IQ Local Store, it must also be shut down.