When ShareGate Migrate copies list items, there is no implicit way to know if the item being copied already exists in the destination of your migration, so it uses key properties to avoid overwriting items.
Note: Key properties can only be changed on a list. Library migrations rely on the file name, which is always unique to each document.
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You can set ShareGate Migrate to handle already existing content in different ways. For instance, you can copy and replace existing items at the destination or copy only newer items (incremental copy).
These actions require the application to determine what items match the source and the destination.
To do so, ShareGate Migrate relies on the properties Title and Created since they are default properties and usually offer a unique value on every list item.
Note: Calendar items have key properties as well, but they are different than those of list items. These properties are Created, Recurrence, Start time, and Title.
When should you change key properties?
You will have to select new key properties if you're dealing with one of the examples below:
Multiple list items have the same values in the Created and Title fields. For example, some lists will not use Title, and something like a workflow operation can leave multiple items with the same Created value.
The key properties were set on other properties that don't have a unique value for each list item.
Note: your list item IDs cannot be used as a key property because they are not always preserved in the destination list.
How to change your key properties
You can find your key properties in the Property mappings screen with Copy content only.
Select Copy from the menu.
Select Copy content only and connect to a source and a destination.
Click Mappings on the top-right.
Select the Properties tab.
Click on the key icons next to the source properties to add or remove key properties.
A filled yellow key indicates a key property, while an outlined key indicates a property that is not a key property.
Click Save.