V-VOLs are virtual volumes that do not have any physical storage space. Thin Image Advanced uses data reduction shared volumes (DRS-VOLs) as V-VOLs.
Thin Image Advanced uses S-VOLs to access snapshot data from hosts. You can use only DRS-VOLs for S-VOLs. Therefore, if you use snapshot pairs (a pair with the snapshot attribute) to access snapshot data from hosts, then DRS-VOLs are required to create Thin Image Advanced pairs or assign an S-VOL to snapshot data. If the storage system or snapshot pair does not need access to snapshot data from hosts, DRS-VOLs are not necessary.
You can release the DRS-VOLs that are being used as Thin Image Advanced S-VOLs from assignment of snapshot data. Released DRS-VOLs can be assigned to other snapshot data. However, you cannot release assignment of DRS-VOLs used as node volumes to snapshot data or assign the DRS-VOL to different snapshot data.
If you release a DRS-VOL being used as a Thin Image Advanced S-VOL from assignment to snapshot data, and then assign the DRS-VOL to different snapshot data, this DRS-VOL becomes the S-VOL of another pair. Therefore, each time you assign a DRS-VOL to snapshot data, execute the command that allows the host server to recognize the device.
You cannot release definitions of DRS-VOLs if the DRS-VOLs are being used as Thin Image Advanced secondary volumes; you must first release the Thin Image Advanced pairs that are using the DRS-VOLs.