Incremental copy is a migration option in your Operation mode settings that will replace an item at the destination only if the date modified field is older than that at the source, and copy new items from the source that don't exist at the destination. This aims to ensure that you are not overwriting newer files at the destination.
This article will take you through the default behavior of Incremental copy, so you can decide if it is the right option for your oncoming migration project.
- How it works
- Folder hierarchy
- Large lists or libraries
- Documents that were deleted at the source
- Incremental Copy Structure
How it works
With Copy if newer (incremental), the ShareGate migration tool analyses your source and destination list or library to determine which items or documents should be copied or updated.
The ShareGate migration tool considers a file a match when it has the same file name in the source and destination library. It considers a list item a match when it has the same title and created date in the source and destination list.
If no match is found, the item is copied as a new item at the destination.
If a match is found, the ShareGate migration tool looks at the last modified date to determine if the item should be updated or ignored at the destination.
- Title and Created are the default key properties for list items. If you have a list where your titles are not unique, the ShareGate migration tool will not be able to determine what items match between your source and destination. In such a case, you can change the key properties and use a property that has unique values for each item instead. You have to use Copy content to change key properties.
- If the matching item at the destination is deleted or moved to a different folder or library, the incremental copy will not find the item and it will be recreated in the original location.
If your destination library does not have the same folder hierarchy as your source, the ShareGate migration tool will not be able to find documents that are in different folders at the destination. This can result in some files and folders being duplicated at the destination.
Large lists or libraries
Incremental Copy is not designed for large lists or document libraries. In this mode, the ShareGate migration tool crawls the source and destination to read your content in batches of 1000 items at a time to determine what needs to be copied. So if you have more than a couple of thousand items, the ShareGate migration tool will need to make many calls to obtain the data. This can result in your migration job going slowly or being unable to start altogether due to performance issues or throttling (on Microsoft 365).
If you are migrating a large list or document library, we recommend using Copy and replace, setting your Filter options to enable Time range filter, and setting the time frame to limit your migration to elements created or modified in your chosen range.
If versioning is enabled, the ShareGate migration tool will add the new versions from the source at the destination. If the versioning is disabled, the destination item will be replaced.
Note: When using Insane Mode on Microsoft 365, all versions at the destination will be replaced by the versions from the source because of a limitation in the Azure Import API.
Documents that were deleted at the source
Incremental Copy is not meant as a full synchronization option, and will not identify or delete items at the destination that were deleted at the source. This avoids any potential data loss during the migration process. You will need to manually delete those items once your migration is complete.
Incremental Copy structure
When using Incremental Copy in a Copy structure migration job, the ShareGate migration tool will only consider List Items and Documents. Any structural element is still rebuilt based on the source since SharePoint doesn't keep an accessible record of your library, list, site changes, and settings.
Incremental Copy does not check for permission changes from the source to the destination. It only validates the last modified date when copying.