Diagnosis
You tried to gain write access to a migration task or to an objectbelonging to it that has the status READONLY.
This is not possible because this migration task is not in change modeand so required locks were not acquired, or rather could not beacquired.

Procedure
Select the migration task again. To do this, first choose anothermigration task momentarily, if required, or exit the transaction andthen call it again.
Further Information about the Locking Properties ofMigration Tasks