live storage migration using blockcopy

[Jing-Wei Su]

Hello,

I'm seeking the solution to live storage migration using blockcopy.
Previously, the "virsh undefine" is required before blockcopy.
https://www.redhat.com/archives/libvirt-users/2015-October/msg00027.html

QEMU has "block-dirty-bitmap-*" operations now, are there steps for
the live storage migration using blockcopy without undefine?

By the way, why's the purpose of "undefine" before blockcopy?
Thanks.

Sincerely,
Jing-Wei