A data storage system provides a method and apparatus for preserving consistency between a database back-up and a set of storage volumes. The system includes a storage manager, or storage controller, interconnected to a plurality of storage volumes, a drive, and a database storage. The storage manager receives data files from an attached data processing unit. The storage manager directs the data files such that the files are written to a selected storage volume loaded into the drive. The storage manager maintains reference information and storage volume location information for each data file in the database storage. The storage manager detects a volume full condition when the storage media approaches a predetermined position prior to the physical end of the volume. The storage manager generates a back-up copy of the current database, transfers the database back-up to the drive, and directs the drive to write the database back-up onto the selected storage volume. Thus, each selected storage volume contains a database back-up which remains consistent with the data files currently stored on the selected storage volume and previously stored on previously selected storage volumes.