You cannot reduce the size of a volume. If you try to reduce the size, an error message is  displayed. CKD volumes can be deleted by using the  rmckdvol  command. FB volumes can be deleted  by using the  rmfbvol  command. The command includes a capability to prevent the accidental deletion of volumes that are in  use. A CKD volume is considered  in use  if it participates in a Copy Services relationship, or if  the IBM z Systems path mask indicates that the volume is in a grouped state or online to any  host system.  If the  -force  parameter is not specified with the command, volumes that are in use are not  deleted. If multiple volumes are specified and several volumes are in use and several volumes  are not, the volumes that are not in use are deleted.  If the  -force  parameter is specified on the command, the volumes are deleted without  checking to see whether they are in use.  Example 12-68 shows trying to delete two volumes, 0900 and 0901. Volume 0900 is online to  a host. Volume 0901 is not online to any host and not in a Copy Services relationship. The  rmckdvol 0900-0901  command deletes only volume 0901, which is offline. To delete  volume 0900, use the  -force  parameter. dscli>  lsckdvol 0900-0901 Name ID accstate datastate configstate deviceMTM voltype orgbvols extpool cap (cyl) ======================================================================================== ITSO_J 0900 Online Normal Normal 3390-9 CKD Base - P1 10017 ITSO_J 0901 Online Normal Normal 3390-9 CKD Base - P1 10017 dscli>  rmckdvol -quiet 0900-0901 CMUN02948E rmckdvol: 0900: The Delete logical volume task cannot be initiated because the  Allow Host Pre-check Control Switch is set to true and the volume that you have specified  is online to a host. CMUC00024I rmckdvol: CKD volume 0901 successfully deleted. dscli>  lsckdvol 0900-0901 Name ID accstate datastate configstate deviceMTM voltype orgbvols extpool cap (cyl) ======================================================================================== ITSO_J 0900 Online Normal Normal 3390-9 CKD Base - P1 10017 dscli>  rmckdvol -force 0900 CMUC00023W rmckdvol: Are you sure you want to delete CKD volume 0900? [y/n]: y CMUC00024I rmckdvol: CKD volume 0900 successfully deleted. dscli>  lsckdvol 0900-0901 CMUC00234I lsckdvol: No CKD Volume found. Example 12-68 Delete CKD volumes Chapter 12. Configuration with the command-line interface  427 etmonpauseremain - etmonitorreset unknown ==============Rank extents============== rank extents capacity (MiB/cyl) =============================== R3 236 262668