Storage management software in the system manages the contents of the tape volume cache. Virtual tape volumes are migrated from the tape volume cache to physical tape when they are no longer needed for fast access and recalled from tape to the tape volume cache when they are again requested to be mounted. The storage management software stacks multiple migrated files onto a native tape, thereby utilizing its storage capacity. For more information on this volume stacking concept, see Emulating 3490-type virtual volumes.