Abstract: A method for modifying system configuration data sets in a telecommunications switching system that has first function modules (SWU-ADS) for processing switching-oriented and/or administration and maintenance procedures and second peripheral function modules (VMS, ETB) for realizing supplementary performance features. For producing data consistency, backup copies are produced of the content of at least a part of the databases and administration and maintenance commands that modify database contents and that are subsequently input into the system, are listed in the form of command information in the chronological sequence of their occurrence. Every command information is supplemented with a database-associated information that indicates the implementation or non-implementation of the respective administration and maintenance command.