A Generation Data Group (GDG) is a group of chronologically or functionally related datasets that are processed periodically by adding new generations and retaining or discarding old generations. A GDG base is created using IDCAMS utility to define the base and track generation numbers. A model dataset provides DCB parameters for the GDG and must be cataloged. GDGs can be concatenated by specifying each dataset name and generation number, or omitting the generation number to include all generations. A new GDG is coded as (+1) after the dataset name to push down existing generations by one level.