text: **7.8.18 Shrinking a volume**
  
  The**shrinkvdisksize**command reduces the capacity that is allocated to the particular 
  volume by the specified amount. You cannot shrink the real size of a thin-provisioned volume 
  to less than its used size. All capacities (including changes) must be in multiples of 512 bytes. 
  An entire extent is reserved even if it is only partially used. The default capacity units are 
  MBs. 
  
  You can use this command to shrink the physical capacity of a volume or to reduce the virtual 
  capacity of a thin-provisioned volume without altering the physical capacity assigned to the 
  volume. Use the following parameters to change volume size: 
  
  (cid:2) For a fully provisioned volume, use the**-size**parameter. 
  (cid:2) For a thin-provisioned volume’s real capacity, use the**-rsize**parameter. 
  (cid:2) For a thin-provisioned volume’s virtual capacity, use the**-size**parameter. 
  
  When the virtual capacity of a thin-provisioned volume is changed, the warning threshold is 
  automatically scaled. 
  
  If the volume contains data that is being used, do not shrink the volume without backing up 
  the data first. The system reduces the capacity of the volume by removing arbitrarily chosen 
  extent, or extents from those sets allocated to the volume. You cannot control which extents 
  are removed. Therefore, you cannot assume that it is unused space that is removed. 