When you create a VMFS5 datastore on a device that supports the atomic test and set (ATS) locking, the datastore uses the ATS-only locking mechanism. In certain circumstances, you might need to downgrade the ATS-only locking to ATS+SCSI.

You might need to switch to the ATS+SCSI locking mechanism when, for example, your storage device is downgraded. Or when firmware updates fail and the device no longer supports ATS.

The downgrade process is similar to the ATS-only upgrade. As with the upgrade, depending on your storage configuration, you can perform the downgrade in online or offline mode.

Note: If you are running a VMware vSAN environment or have ATS-only VMFS volumes, do not deactivate ATS. Deactivating ATS might result in an outage as no locking mechanism is available. For more information, see a VMware Knowledge Base article.


  1. Change the locking mechanism to ATS+SCSI by running the following command:
    esxcli storage vmfs lockmode set -s|--scsi -l|--volume-label= VMFS label -u|--volume-uuid= VMFS UUID.
  2. For an online mode, close the datastore on all hosts that have access to the datastore, so that the hosts can recognize the change.