As i get some questions about it in recent times: With a normal SATA/SAS disk you can simply unplug a disk without warning and preparation. NVMe are different. For all practical purposes they are PCI devices. And they want to be handled as such. Unplugging a NVMe drive without using the proper procedure is pretty much like yanking out a PCI card without preparation. So when you want to remove a NVMe disk you have to use the hotplug command in Solaris. To cite the documentation:
On a Oracle server a “OK to remove” light will turn on. Now it should appear as empty.
For replacement, wait 10 seconds after removal. Then insert the new NVMe drive. You have to enable it before using it.