IDMS/DC system mode program assembler ends with RC=4 and:
** ASMA254I *** MNOTE *** 55+ 4,MPMODE HAS BEEN OMITTED, "MPMODE=CALLER" ASSUMED.
Release : 19.0
To resolve the problem so the assembler ends with RC=0, add MPMODE=CALLER to the #START macro:
label #START MPMODE=CALLER
See documentation section Macros Required for DC/UCF Calling Conventions