Be aware when you have APEX in your databases installed - and especially if you ACTIVELY use APEX - it may be a very good idea to upgrade APEX upfront without causing downtime for your entire database.
What do you think when you see this post-upgrade result?
Oracle Database 12.1 Post-Upgrade Status Tool 08-07-2015 15:08:26
Component Current Version Elapsed Time
Name Status Number HH:MM:SS
Oracle Server UPGRADED 220.127.116.11.0 00:19:26
JServer JAVA Virtual Machine VALID 18.104.22.168.0 00:10:52
Oracle Workspace Manager VALID 22.214.171.124.0 00:01:52
OLAP Analytic Workspace VALID 126.96.36.199.0 00:00:34
OLAP Catalog OPTION OFF 188.8.131.52.0 00:00:00
Oracle OLAP API VALID 184.108.40.206.0 00:00:42
Oracle XDK VALID 220.127.116.11.0 00:01:07
Oracle Text VALID 18.104.22.168.0 00:01:36
Oracle XML Database VALID 22.214.171.124.0 00:03:55
Oracle Database Java Packages VALID 126.96.36.199.0 00:00:22
Oracle Multimedia VALID 188.8.131.52.0 00:03:57
Spatial UPGRADED 184.108.40.206.0 00:08:56
Oracle Application Express VALID 4.2.5.00.08 00:46:19
Final Actions 00:03:48
Total Upgrade Time: 01:44:16
I've got a bit worried as the time to upgrade APEX took 44% of the complete database upgrade downtime. APEX (Oracle Application Express) is a fantastic piece of software which is still completely underrated - potentially because it is for free for everybody who has an Oracle Database license. And things not costing anything are just worth nothing, ey?
Simply be aware when you have APEX in your databases installed - and especially if you ACTIVELY use APEX - it may be a very good idea to upgrade APEX upfront without causing downtime for your entire database.
See this blog post here about how to upgrade APEX upfront:
Source: Upgrade Your Database