The Upgrade History module tracks every upgrade made to an instance. Administrators can use the module to resolve upgrade conflicts and optionally to revert customizations to base system versions to take advantage of new features.

An upgrade history record is created for each upgrade that is run. To view an upgrade history record, navigate to System Diagnostics > Upgrade History and click the upgrade.
Note: Debug Upgrade provides detailed debugging output for transactions containing artifacts affected by the most recent upgrade, and is designed to assist in upgrade error resolution. See Debug upgrade.
Note: The Payload and Payload Hash fields have been removed from the Upgrade History record in a previous release.

Review Skipped Records form section

The Skipped Changes to Review related list displays each record that was skipped during the upgrade process. Use the list to review the reason for each skipped record in the list and then either merge your customization or revert your customization to the base system.