# Update or Remove References and Databases

To update or remove an image comparison reference use the following actions:

- To add, remove, or update custom metadata for a reference, use the actions `AddImageComparisonMetadata`, `RemoveImageComparisonMetadata`, and `UpdateImageComparison` `Metadata`.
- To retrieve the training image from an image comparison reference, use the action `GetImageComparisonReferenceImage`.
- To change the identifier of a reference you added to an image comparison database, use the action `RenameImageComparisonReference`.
- To change the label of an image that you added to a reference, use the action `RelabelImageComparisonReferenceImage`.
- To move an image comparison reference to a different database, use the action `MoveImageComparisonReference`.
- To remove a reference from a database and discard the training image and all associated metadata, use the action `RemoveImageComparisonReference`.

To update or remove change detection databases, use the following actions:

- To rename a database, use the action `RenameImageComparisonDatabase`.
- To delete an image comparison database and all of the information that it contains, use the action `RemoveImageComparisonDatabase`.

For more information about the actions that you can use to train Media Server, refer to the Media Server Reference.

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