Is it possible to upgrade JIRA from version 4.4.4 to 6.4 directly? Is the procedure the standard or do I have to do something different?
Yes, it is.
You can just follow whichever upgrade method suits you better as described on: https://confluence.atlassian.com/display/JIRA/Upgrading+JIRA
Cheers,Matheus
It looks like you're new here. Sign in or register to get started.