When you delete a logical volume, the Oracle FS System reconditions the space (by writing a predefined bit pattern) before reclaiming the space for reuse. As the previously allocated capacity frees up, the capacity becomes available for allocation.
When you delete a large volume, the operation can take awhile for all of the capacity to be reclaimed. When deleting auto-tiered LUNs, you can quickly reclaim the allocated capacity by manually compacting the Storage Domain. Compacting releases unused allocated space for autotiered LUNs and makes that space available to the Oracle FS System. The system automatically compacts the Storage Domain when the allocated space for auto-tiered LUNs reaches 20%.
Because of the additional time that is needed to recondition the drives holding the volume data, the amount of physically allocated capacity plus the amount of physically free capacity in the owning drive groups might not equal the total physical capacity in those drive groups. Therefore, while the deleted capacity is being reconditioned, Oracle FS System Manager (GUI) displays the amount of physical capacity that remains to be reconditioned as “preparing.”