Because of limitations in MTC of one migration plan per namespace, it is imperative to clean up the migration plan after the migration completes. If you don't this makes it so no other VMs in that namespace can be storage live migrated. Once we switch to the OCP-V migration orchestrator this limitation will be removed, but we have to deal with it right now.

OCP-V 4.19.0-RC6

100%

1. Create a migration using the wizard in the UI.
2. Wait for it to complete.
3. Look in the storage migration plans list, and see the migration completed there. Now it is impossible to migrate another VM in the same namespace.

Only one migration is possible per namespace until a migration plan is deleted.

I can migrate VMs from the same namespace at will.

There are 2 possible mechanisms to achieve this with the known MTC limitation.
1. Immediately delete the migration plan after completion, at which point the list of migration plans is kind of useless.
2. Before creating another migration plan detect if there are any migration completed migration plans for the same namespace. If so delete those migration plans before creating the new one.

As a side note which is also important because it will cause confusion when MTC completes a migration, it will mark the SOURCE PVC with a label indicating it was the source of a migration (the key of the label will be migration.openshift.io/source-for-directvolumemigration). If one tries to migrate back to the original PVC, this label confuses new migration plans, and in my testing I ended up with migration plans that had 0 PVs selected since the only PVC had that label and was excluded. I suggest that when we remove the migration plan (either option) we also remove the label from the PVC so we don't get this issue.