## 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. 

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. 

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. 

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 

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. 

