1. A method for accurately calculating database space for an IMS OSAM dataset the method comprising the steps of: monitoring an order in which a large physical sequential data file, which is an IMS OSAM dataset, is stored to multiple logical devices, each of which has an allocatable volume; analyzing the large physical sequential data file to determine a volume of said file stored in the allocatable volume of each of the multiple logical devices; determining a total volume stored for the large physical sequential data file from said determined volumes; and determining if the total volume exceeds a predetermined threshold which is a percentage of the total allocatable volumes of said multiple logical devices.