@kosa7 from what the XO devs told me :
for now you have to handle it completly manually, since we have separated collection a not a relationnal db...
You could maybe use a smart mode backup with a VM tag.
We plan to implement a relational database in the future, which would at least offer the possibility to handle this.
"Reasonnably :
warm migration should be more a one off , so the user must handle the consequence.
If he uses this regularly, he should add a tag to the VM " DBPRODBACKUPPLZ" and then configure his job to use this tag"
FYI @olivierlambert