A question about oracle upgrade from 12.0.0.1 to 12.0.0.2 using dbua I found this guide for upgrade.
After the upgrade, can I delete safely the old DB product dir
/var/oracle/app/oracle/product/12.1.0 ?
Yes, but do not simply delete it - deinstall it properly: http://docs.oracle.com/database/121/LADBI/remove_oracle_sw.htm#LADBI7824

Run $ORACLE_HOME/deinstall/deinstall and follow the instructions.