A U4039 user abend in module CEEPLPKA can occur, if multiple CA Spool C:D nodes attempts to transfer multiple files at the same time.
CA Spool release 11.6 systems running under any releases of z/OS and IBM Connect:Direct.
The IBM Connect:Direct API does not support multiple threads.
Enqueue/Dequeue logic has been added to force C:D and CA XCOM transfers to be single threaded.
CA Spool release 11.6 PTF RO23111 forces both C:D and XCOM transfers to be single threaded. Solution has been sourced on releases 11.7 and up.