A method for storing data includes establishing an extended generation group comprising a plurality of data sets. The plurality of data sets includes a first data set containing primary members and a first number of generations of each of the primary members, and a second data set containing a second number of generations of each of the primary members. The method further indicates, in the metadata of the first data set, a maximum number of generations allowable in each of the first and second data sets When a primary member is modified in the first data set, the method automatically moves an oldest generation in the first data set to the second data set, and deletes an oldest generation in the second data set to ensure that the extended generation group does not exceed the maximum number.