It is expected that when an production version is locked in ECC, then its PDS is to be deleted in APO. But so far we have a note 854561 that provides a work around solution, by setting the procurement priority of a locked PDS to 555555… and then this value is filtered during source determination. From business point of view it makes no difference whether the PDS does not exist anymore (i.e. was deleted) or is just filtered (was locked). Some time the PDS will not be used anymore by existing orders, so some time the deletion will work eventually.
There are 2 new notes 2167226 and 2167228, which actually make use of a lock indicator It works exactly the same way as note 854561, but a) is part of standard and b) use an appropriate field (no misuse of procurement priority).
So if you face issues in deletion of locked production version then please implement these notes