Upgrading to Oracle 12c - Expert Consolidation in Oracle Database 12c - page 433

Upgrading the database with the Database Upgrade Assistant
After having experienced what happens during a database migration many database administrators might prefer to
use a graphical tool for the same job for smaller, not quite as important databases. After all, the DBUA utility has been
developed by Oracle to provide a means of upgrading databases repeatedly, in the same way without overlooking
details. The code in DBUA will certainly be executed over and over, no matter if it is the first, second or tenth database
you are upgrading.
Nevertheless the same precautions as described earlier in the context of the manual database migration have to
be taken. Do not become lazy-there is nothing worse than a corrupt database that is stuck halfway between 11.2.0.3
and 12.1 and cannot be recovered.
It is recommended that the database you want to upgrade be running before DBUA is invoked. This ensures that
the database has been started using the correct parameter files. Remember that DBUA will restart the database during
the upgrade process using the default parameter files, so these need to be correctly configured. The interactive Database
Upgrade Assistant requires an X server to connect to. Please refer back to chapter 5 for a refresher on how to provide
an X-environment for a graphical Oracle utility if you are unsure how to proceed. The standard way of presenting
X-applications to the database administrator in this topic is vncserver. Using the vnc client to connect to the server in
question you can start the DBUA in an X-terminal. Start the Upgrade Assistant from the 12.1 Oracle home. You will be
surprised how flexible and useful the upgrade assistant has become! When started it will greet you as shown in Figure 12-7 :
Figure 12-7. DBUA welcome screen