Thank you for your help.

(just want to make sure)
Going to Oracle 8.1.5 from 8.0.6 is a migration and from 8.1.5 to 8.1.6 is upgrade. Is that right?

How do you usually prepare for this process?
I guess that if I use Oracle Migration Utility, It could be a very simple process, but I red about lots of problems in Meta Link after migration or upgrading database. I am a little bit nervous.