Finally I started my owm R12 uprgade last week.
I installed 188.8.131.52 on Oracle Linux 5, so I could upgrade this environment to R12.
At this moment I am installing the upgrade pacth for R12.
After installing the vision environment 11i, I used the rapidwiz to create the R12 environment on that same machine.
I will post al the upgrade steps when I am finished upgrading...