Is there any functionality impact in upgrading from jira v6.4.12 to v.7.1.8

[Amir Vegdani]

We are looking to upgrade JIRA from version 6.4.12 to version 7.1.8

Is there any functionality impact, that users or admin might face.

Let me ask it other way as well.

Is there any function (user and administrators) that was available in 6.4.12, which is decommissioned in 7.1.8 

[Nic Brough -Adaptavist-]

Yes.  Please read through the migration hub and release notes to see what has changed.

https://confluence.atlassian.com/migration/jira-7 - this covers the structural changes that happen between 6 and 7. 

Release notes for JIRA Software 7.0 - https://confluence.atlassian.com/jirasoftware/jira-software-7-0-x-release-notes-776997721.html
Release notes for JIRA Software 7.1 - https://confluence.atlassian.com/jirasoftware/jira-software-7-1-x-release-notes-788728210.html