Abstract: A method of reorganizing an IMS database. The method creates, in a storage device, a header data structure containing information about the size and key structure of the database. Next, the number of sequential files to be used for temporary storage of data from the database and the desired number of parallel unload processes to be used in unloading the database are determined. Then, the desired number of unload processes are initiated. These unload processes copy data from the IMS database to one or more sequential files so that hierarchically-related data in the database is copied in sequence. Next, a storage space to contain the IMS database is provided and address ranges of the storage space to the sequential files are assigned. Finally, a plurality of concurrent load processes are initiated. These load processes write data from the specified sequential files to the storage space at the respective address ranges assigned to the specified sequential files.