And another thing:
uid=1027(prdadm) gid=1004(sapsys) groups=1004(sapsys),1005(oinstall),1006(oradba),1107(dba),1008(oper),1009(sapinst),1010(asmoper),1012(asmdba)
So <sid>adm belongs to dba, oper, asmoper, asmdba.
The system in question is an OEL Linux system. <sid>adm is managed by a directory. I think AD. User Oracle is not.
I have been told that AD only manages the primary group - other group assignments are totally under the control of the /etc/groups file. That's what I've been told.
R