I googled to set the coredump max size on AIX to 20 MBytes: 0:root@SERVER:/root # su - username$ ulimit -atime(seconds)        unlimitedfile(blocks)         unlimiteddata(kbytes)         131072stack(kbytes)        32768memory(kbytes)       32768coredump(blocks)     2097151nofiles(descriptors) 2000threads(per process) unlimitedprocesses(per user)  unlimited$ exit0:root@SERVER:/root # chuser core=40960 username0:root@SERVER:/root # su - username             $ ulimit -atime(seconds)        unlimitedfile(blocks)         unlimiteddata(kbytes)         131072stack(kbytes)        32768memory(kbytes)       32768coredump(blocks)     40960nofiles(descriptors) 2000threads(per process) unlimitedprocesses(per user)  unlimited$ exit0:root@SERVER:/root # but later a coredump, sized about ~800 MByte was created by this user.My question: Why? Is the 40960=20MB? -> 1=0,5 KByte? Or could was that the problem that the user probably didn't logged out/in after the max coredump size change?
Setting max coredump size on AIX doesn't work
aix
The process which created the core dump was probably started before you changed the ulimit, and hence was running from a shell or environment with the old setting.