Upgrading to Oracle 12c - Expert Consolidation in Oracle Database 12c - page 437

Gather Statistics Before Upgrade. If your dictionary statistics are stale the migration can
take longer than necessary to complete. If you tick the “gather statistics before upgrade”
check box then DBUA will perform this step for you. If you have recent and accurate
dictionary statistics this might not be needed.
Set User Tablespaces Read Only During Upgrade. This is a useful option during the
migration to prevent any changes to the SCNs marked in the datafile headers, allowing for a
much shorter RMAN restore should something go wrong during the migration.
File Locations. You can specify new file locations of the diagnostic destionation
and audit dumps. Remember that the “diag” directory will be created automatically;
if you enter $ORACLE_BASE/diag as the diagnostic destination, you will end up with
$ORACLE_BASE/diag/diag/ which is probably not what you intended.
You have another option to run your own scripts before and after the database upgrade in the “custom scripts”
pane, which is not shown here. A click on the “Next” Button leads to the “Management Options” screen which is
not shown. It allows you to configure the database either for OEM Database Express which replaces OEM Database
Console or alternatively with Enterprise Manager 12c Cloud Control. If you wish to register the database with Cloud
Control you need to have an appropriately configured agent installed on the host. If you do not want to configure
these options at this time click on “Next” will guide you to the screen shown in Figure 12-11 :
Figure 12-11. Move Database Files as part of the upgrade