If you would like to upgrade the database via CLI interface, you may refer to this post: How to Move 11.2.0.2 Database to 11.2.0.4 Environment and Upgrade
When we have already prepared the environment for the database to upgrade, then we can initiate DBUA.
[oracle@db11204 ~]$ dbua
Oracle Database 11g DBUA - 01
Oracle Database 11g DBUA - 02
Oracle Database 11g DBUA - 03
Oracle Database 11g DBUA - 04
Oracle Database 11g DBUA - 05
Oracle Database 11g DBUA - 06
Oracle Database 11g DBUA - 07
Oracle Database 11g DBUA - 08-1
Oracle Database 11g DBUA - 08-2
Oracle Database 11g DBUA - 08-3
Oracle Database 11g DBUA - 08-4
Oracle Database 11g DBUA - 09-1
Oracle Database 11g DBUA - 09-2
Oracle Database 11g DBUA - 09-3
Oracle Database 11g DBUA - 10-1
Oracle Database 11g DBUA - 10-2
Oracle Database 11g DBUA - 10-3
[oracle@db11204 ~]$ dbua
Database upgrade has been completed successfully, and the database is ready to use.
The following document describes important behavioral changes from previous database releases:
/u01/app/oracle/product/11.2.0/dbhome_1/assistants/dbua/doc/DefaultBehaviorChanges.html