"If you are attaching a database with the same name but in a
different group and/or acount as a database already attached to
the DBEnvironment, you must specify an alternative owner name at
attach time."
 
HP IMAGE/SQL Administration Guide
36385-90001
 
So try,
 
ATTACH XYZ.GROUP1.ACCT
ATTACH XYZ.GROUP2.ACCT WITH OWNER=ABC
 
Regards,
Peggy Lacy
HP Database Expert Center