DistCp doesn't check the job-status when run in blocking-mode, before returning its exit-code. (The Yahoo-internal version did this correctly.)
In blocking-mode, DistCp must check that the launched job runs to completion, and return an appropriate exit-code.
Pretty serious bug, since it affects data integrity, in Oozie-launched-DistCp actions.
(I could've sworn I had another JIRA with this patch attached.)