12.4.3 Logical control unit creation When volumes for a CKD environment are created, you must create logical control units  (LCUs) before the volumes are created. In Example 12-59, you can see what happens if you  try to create a CKD volume without creating an LCU first. Example 12-59 Trying to create CKD volumes without creating an LCU first First, use the  mklcu  command. The command uses the following format: mklcu -qty XX -id XX -ss XXXX Note:  For the z/OS hardware definition, the SSID has to be unique for all connected  storage systems. The z/OS hardware admin usually provides the SSID to use. To display the LCUs that you created, use the lslcu  command.  Example 12-60 shows the creation of two LCUs by using the  mklcu  command and then listing  the created LCUs by using the  lslcu  command. By default, the LCUs that were created are  the 3990-6 type.  Because two LCUs were created (by using the parameter  -qty 2 ), the first LCU, which is  ID BC (an even number), is in address group 0, which equates to rank group 0. The second  LCU, which is ID BD (an odd number), is in address group 1, which equates to rank group 1.  By placing the LCUs into both address groups, performance is maximized by spreading the  workload across both servers in the DS8880. Important:  For the DS8880, the CKD LCUs can be ID 00 to ID FE. The LCUs fit into one of  16 address groups. Address group 0 is LCUs 00 to 0F, address group 1 is LCUs 10 to 1F,  and so on, except group F is F0 - FE. If you create a CKD LCU in an address group, that  address group cannot be used for FB volumes. Likewise, if, for example, FB volumes were  in LSS 40 to 4F (address group 4), that address group cannot be used for CKD. Be aware  of this limitation when you plan the volume layout in a mixed FB/CKD DS8880. Each LCU  can manage a maximum of 256 volumes, including alias volumes for the parallel access  volume (PAV) feature. IBM DS8880 Architecture and Implementation 420  Example 12-60 Create a logical control unit with mklcu dscli>  mklcu -qty 2 -id BC -ss BC00 CMUC00017I mklcu: LCU BC successfully created. CMUC00017I mklcu: LCU BD successfully created. dscli>  lslcu ID Group addrgrp confgvols subsys conbasetype ============================================= BC 0 C 0 0xBC00 3990-6 BD 1 C 0 0xBC01 3990-6 dscli> mkckdvol -extpool p2 -cap 262668 -name ITSO_EAV1_#h C200 CMUN02282E mkckdvol: C200: Unable to create CKD logical volume: CKD volumes require a CKD  logical subsystem.