Hello.
A couple of days ago I performed an upgrade from Jira 4.4.1 to Jira 4.4.5.
My Jira is using MyQSL 5.5.
I created the database with the following command (as referred in the documentation):
create database jiradb character set utf8;
(DOcumentation: create database jiradb character set utf8;).
When I run the Jira 4.4.5 Installer I get this message: "Upgrade Check List. Backup your external database: Your Jira database will be incompatible with your existing Jira Version..."

In here I choose next and I was able to make the upgrade successfully.
I don't understand why did i got this message. Is this only a reminder to check database compatibility?
What does this mean?