If you are upgrading from a version lower than 3.2, this implies that an upgrade task will run to pre-calculate historical data. This one-time action will run in the background so that Xray remains available during the upgrade. A  re-index operation of your Jira instance is required to make the internal data searchable and usable by Xray.

If upgrading from v3.2.x or v3.3.x to v7, you must recalculate data in the Xray configuration section → Custom Fields. This recalculation is necessary because of the huge improvement in the amount of data that Xray needs to add to the table and the Lucene indexes.

Downgrading from Xray 7.x.x to a previous version may have the following side effects:

After creating some specific data using Test Case Versions, the user may have some glitches when downgrading to a specific version of Xray

• On a Test Issue, multiple manual test versions with steps, when downgrading the test issue will show all steps from all the versions
• On a Test Issue, multiple manual test versions with specific datasets, when downgrading the test issue will show the parameters from all the datasets 
• On a Test issue, having different test versions linked to the same precondition issue when downgrading, the test issue will show an integrity error instead of showing the precondition table
  
  
  And the precondition will show the warning of being linked to an archived test