Before migration - requirements and understand limitations

Not all data from The Scheduler Server (or DC) is migrated to Cloud.

Enable migration dev mode
Go to page <jira-server-base-url>/secure/admin/SiteDarkFeatures!default.jspa and add migration-assistant.app-migration.dev-mode in text box and submit (it allows you to test migration path)

Calendars (global & project)
Calendars in cloud are a bit simpler and limited by the way data can be stored.
Scheduled Issues ownership
In Server/DC there is a ‘creator’, and templates can be shared with other users.
In Cloud everyone with access to app in project has the same rights and The Scheduler is the ‘creator’.
Execution history
There is a difference in recognition if issue was created by app, not everything can be restored on Cloud.
You won’t see all issues created from particular SI.
Text formatting
For example when you migrate bolded text in description field then after migration you will get it’s text representation (in this case *Text*)

Max 10 subtasks
When you migrate Scheduled Issue with more than 10 subtasks, only 10 will be migrated. 10 subtasks is the app limit.
Note: On request, we can increase your subtasks limit, but it won’t affect migration process limitation.

Clean up
Remove not used templates, if you are keeping old templates just to have access to that template execution history - it won’t be migrated. That’s why it is better to build some Jira filter or add some new/special label to mark those issues
Clean up, again
Migration is a great opportunity to make some adjustments and removal of not used templates. Again remove unnecessary and not used templates.