Horizon Instant Clones provisioning fails with the error: "Unable to prepare migration"
Updated: Aug 4, 2019
Sometimes we have face this issue while creating instant clone pool.
If you have already tried to set Esxi hosts in maintenance mode ,even set attribute instantclone.maintenance=2 but still you are facing same error.
This KB if you have already followed : https://kb.vmware.com/s/article/60397
Then try this workaround : Power off your parent template , go to edit settings => VM options => Advanced => edit configuration => remove any value against this attribute "namespaceMgr.db".
=> Power ON parent VM
=> Gracefully shutdown and take new snapshot.
=> Publish new snapshot in Instant clone pool