A stacked volume is a volume in a virtual tape server library that is used to store one or more logical volumes. When stacked volume support is not enabled, DFSMSrmm does not track stacked volumes, but allows you to define them to DFSMSrmm. DFSMSrmm records the name of the exported stacked volume as the 'In container' information for each logical volume. DFSMSrmm keeps track of the 'In container' information only while the logical volume is exported.