Creating logical control units for CKD volumes using DS CLI

The logical control unit (LCU) is the S/390 and zSeries host equivalent of the logical subsystem (LSS) for open systems hosts. The LCU must be defined (created) before CKD logical volumes can be created.

The DS6000 has a 16 384 volume address space that is partitioned into 64 logical subsystem (LSS) units, where each LSS contains 256 logical volume numbers. The 64 LSS units are assigned to one of 4 address groups, where each address group contains 16 LSSs, or 4096 volume addresses. All of the LSSs in one address group must be of the same type (CKD or fixed block).

Typically, LCUs are created in groups of 16, beginning at LSS address X’x0’.

Use the lsaddressgrp, mklcu, and lslcu commands to create the LCU type logical subsystems. You must be logged into the DS CLI application and connected to the storage unit that will be used for open systems host system storage.

To create LCUs, perform the following steps:

Find unassigned and available address groups by issuing the lsaddressgrp command. To use the lsaddressgrp command, type the following at the dscli command prompt:
```
dscli>lsaddressgrp -dev IBM.1750-75FA120
```
This command displays a report on the status of the address groups within your storage unit.
Analyze the report to identify all of the address groups that are available to be defined. Use the following criteria:
- If the list is empty, all of the address groups are available to be defined.
- A defined address group with the storage type fb (fixed block) is not available to be defined.
- A defined address group with the storage type ckd and with fewer than 16 LSSs is available for LCU definition.
- If you are using an undefined address group to make new LCUs, select the lowest numbered address group that is not defined.
- If you are defining a new LCU in an existing CKD address group, use the lslcu command to identify LCUs that are already defined in the target address group.
Make the LCU logical subsystem objects by issuing the mklcu command. Type the command using the following format at the dscli command prompt:
```
dscli>mklcu –dev IBM.1750-75FA120 -qty 16 -id 00 -ss 0010 -lcutype 3390-3
```
In this example, the values specify the following:
qty

Specifies the number of LCU IDs to be created.

id

Specifies the LCU ID to be created, or the first LCU ID in a sequence of LCU IDs to be created.

ss

Specifies the subsystem ID that you have assigned. If multiple LCU IDs are being created, then the SSID value increments for each additional LCU ID that is created.
If 16 LCUs are created, starting with SSID 0x10, then the SSID values are 0x0010 – 0x001F.

lcutype
Specifies the type of LCU to be created. You can specify the following types:
- 3390-3
- 3990-tp
- 3990-6
- bs2000
Press Enter. A successful process displays a confirmation message listing each LCU ID number that has been successfully created.
Verify that the LCUs are recognized in the storage unit by issuing the lslcu command at the dscli command prompt as follows:
```
dscli>lslcu -dev IBM.1750-75FA120 -l
```
Using the -l parameter displays a more detailed report for each LCU that is associated with your storage unit.