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Dynamic Multi-Pathing 7.4.1 Administrator's Guide - AIX

Last Published: 2019-02-01

Product(s): InfoScale & Storage Foundation (7.4.1)

Platform: AIX

Manually removing LUNs dynamically from an existing target ID

In this case, a group of LUNs is unmapped from the host HBA ports and an operating system device scan is issued. To add subsequent LUNs seamlessly, perform additional steps to clean up the operating system device tree.

The high-level procedure and the DMP commands are generic.

To remove LUNs dynamically from an existing target ID

Prior to any dynamic reconfiguration, ensure that the dmp_cache_open tunable is set to on. This setting is the default.
```
# vxdmpadm gettune dmp_cache_open
```
If the tunable is set to off, set the dmp_cache_open tunable to on.
```
# vxdmpadm settune dmp_cache_open=on
```
Identify which LUNs to remove from the host. Do one of the following:
- Use Storage Array Management to identify the Array Volume ID (AVID) for the LUNs.
- If the array does not report the AVID, use the LUN index.
For LUNs under VxVM, perform the following steps:
- Evacuate the data from the LUNs using the vxevac command.
  See the vxevac(1M) online manual page.
  After the data has been evacuated, enter the following command to remove the LUNs from the disk group:
```
# vxdg -g diskgroup rmdisk da-name
```
- If the data has not been evacuated and the LUN is part of a subdisk or disk group, enter the following command to remove the LUNs from the disk group. If the disk is part of a shared disk group, you must use the -k option to force the removal.
```
# vxdg -g diskgroup -k rmdisk da-name
```
For LUNs using AIX LVM over DMP devices, remove the device from the LVM volume group.
```
# reducevg vgname
						pvname
```
Using the AVID or LUN index, use Storage Array Management to unmap or unmask the LUNs you identified in step 2.
Remove the LUNs from the vxdisk list. Enter the following command on all nodes in a cluster:
```
# vxdisk rm da-name
```
This is a required step. If you do not perform this step, the DMP device tree shows ghost paths.
Clean up the AIX SCSI device tree for the devices that you removed in step 6.
This step is required. You must clean up the operating system SCSI device tree to release the SCSI target ID for reuse if a new LUN is added to the host later.
Scan the operating system device tree.
Use DMP to perform a device scan. You must perform this operation on all nodes in a cluster. Enter one of the following commands:
- ```
# vxdctl enable
```
- ```
# vxdisk scandisks
```
Refresh the DMP device name database using the following command:
```
# vxddladm assign names
```
Verify that the LUNs were removed cleanly by answering the following questions:
- Is the device tree clean?
  After the LUN is removed cleanly, there should be no hdisk entries in the "Defined" state.
- Were all the appropriate LUNs removed?
  Use the DMP disk reporting tools such as the vxdisk list command output to determine if the LUNs have been cleaned up successfully.
- Is the vxdisk list output correct?
  Verify that the vxdisk list output shows the correct number of paths and does not include any ghost disks.
If the answer to any of these questions is "No," return to step 5 and perform the required steps.
If the answer to all of the questions is "Yes," the LUN remove operation is successful.

More Information

Manually cleaning up the operating system device tree after removing LUNs

Scanning an operating system device tree after adding or removing LUNs