A stacked volume is a volume in a virtual tape server library that is used to store one or more logical volumes.

DFSMSrmm can manage volume movement based on the logical volume or the stacked volume. You control the way DFSMSrmm manages stacked volumes by enabling stacked volume support as described in Enabling stacked volume support. If you do not enable stacked volume support, you can always use the DFSMSrmm TSO subcommands to add, change, or delete information about stacked volumes. You can also perform export, copy export, and import processing of logical volumes, but DFSMSrmm provides no management for the movement of the stacked volumes.

If you do not enable stacked volume support, DFSMSrmm bases volume movement on the logical volume. DFSMSrmm records the stacked volume as the in container value but does not use the stacked volumes to determine volume movement. See DFSMSrmm support for stacked volumes when stacked volume support is not enabled for details about how DFSMSrmm supports stacked volumes when stacked volume support is not enabled.

If you enable stacked volume support, DFSMSrmm tracks stacked volumes and bases volume movement on the stacked volume. See DFSMSrmm support for stacked volumes when stacked volume support is enabled for details about how DFSMSrmm supports stacked volumes when stacked volume support is enabled.

If you define stacked volumes to DFSMSrmm, export, copy export, and import always updates the stacked volume information, regardless of the enablement of stacked volume support

Stacked volumes normally start and end their movement in a VTS automated tape library. The host system is not notified when stacked volumes enter or leave an automated tape library, so the movement of stacked volumes cannot be managed in the same way that physical volumes in an automated tape library are managed.

When you use a DFSMSrmm command for a stacked volume, DFSMSrmm checks both the TCDB and the library manager database to see if the volume is known. If the volume is not known to the library manager, you cannot define the volume as being in the VTS library, but the destination is set to the VTS library name. Once the volume is entered into the VTS, you can use the CHANGEVOLUME subcommand with CONFIRMMOVE to inform DFSMSrmm that the volume is now in the VTS.

When a stacked volume containing exported logical volumes is ejected from the library, as the logical volumes expire, DFSMSrmm places the volumes in pending release status. When the logical volumes are imported back into the library, DFSMSrmm completes the return to scratch process enabling the volumes to be reused. As the exported logical volumes expire, you can do off-site stacked volume management to determine when to bring a stacked volume back on-site for possible reuse. Use REPORT17: Inventory of Stacked Volumes by Percent Active to report on the percentage of active data on a stacked volume and the percentage of active logical volumes on a stacked volume. This EDGRRPTE REXX report, REPORT17, is a helpful tool to aid with stacked volume management. See z/OS DFSMSrmm Reporting for additional information on REPORT17.