Hello Ewa,
 
you might use MPEX as suggested before but you might also check
these ACD-sticky files using MPE/iX commands. Have a look at the
OWNER and GROUPID with :LISTFILE /ACCT/GRP/MYFILE,-3 and check,
if both belong to the account ACCT.
 
If not, then the ACD is mandatory. Even if they look okay you
might try putting them straight with ALTFILE myfile;GROUPID=ACCT;&
;OWNER=someone.ACCT and then try ALTSEC;DELACD again.
 
I have had a customer using an older version of MPEX to change the
file owners of a certain account to MGR.ACCT regularly (because an
application needed this and users sometimes changed it by accident
e.g. using EDITOR as a different user) which had the side effect
of "damaging" the GROUPID field and thus making MPE require the ACD
for the "foreign looking" file then.
 
So try ALTFILE;OWNER;GROUPID before the ALTSEC;DELACD even if things
look nice at first LISTFILE sight. (You need to use HFS name syntax
to have LISTFILE also show the GROUPID, as far as I remember).
 
If you prefer the Posix Shell you can also use "ls -l" and "chown"
and "chgrp" before the (callci) ALTSEC;DELACD.
 
Hope this helps,
 
Lars/iX
 
By the way, the 5.0 Communicator contains an article on the changes
to file security that had to be done for Posix. It takes some work
reading it, but might provide some background information.
 
(Lars Appel, German Response Center, but private here)