Hi Makoto,
Actually what I'm talking about is the hierarchies that seem to be generated when the view is activated. For example lets say my view uses table MKPF and a field called USER. If I unload data from MKPF and perform a data preview on my view I can see data for that column gets loaded into memory. This is not what I'm referring to. What I'm talking about is if you unload MKPF and then go to _SYS_BIC I will see a hierarchy for the USER column much like this;
"_SYS_BIC"."PackageName/MyViewName/HIER/USER"
If you do a data preview on this you will see a hierarchy with a list of DISTINCT users. This is different from performing a data preview on the view because doing this preview does NOT load data into the column of the source table. I can refresh this hierarchy preview repeatedly and it has no affect on the columns in memory for the source table. So my 3 questions are related to this behavior of the automatically generated column hierarchies.
-Patrick