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Don’t migrate all projects at once. It is better to migrate projects in the organization by subtrees from top to bottom. This means to first migrate a Portfolio, after that corresponding Solutions, followed by subordinated ARTs and associated Teams. Then migrate the next portfolio with the same approach until the whole organization is migrated.
Try to migrate parts of your organization with reasonable sizes, like an ART with all teams with e.g. < 50k issues or each project one by onefor all projects to migrate in one batch. Even though the migration helper app is built to handle a large amount of data, predictability, stability and migration speed will be better with reasonable sizes. Potential performance or stability issues do not depend on Jira entities alone, but on the amount of app data entities like custom field values in issues.
If you have already planned future PIs on your Server / DC instance, it is advised to first migrate Solutions and ARTs, then recreate the PIs on your Cloud site in the PI & Iteration Management and then migrate your Team projects. After you migrated the Team projects, you can go to the Agile Hive Project Settings of each Team to the section “Boards & Sprints” and map the automatically migrated sprints to the iterations.
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