This feature is currently in walk.
DISCO deduplicates documents during ingest. When documents are deduplicated, DISCO creates additional instances of that document in the database and combines them into a single document for review. This allows the user to ingest multiple copies of a document, review them all at once, and then produce multiple copies as they were when ingested.
If a review document is deduplicated and you want to overlay only one of the instances, depending on the field—such as the custodian field—you may be required to use an instance-level overlay to identify the documents. For fields such as Custodian, DISCO requires specific identification of the particular instance that needs to be changed.
If a field requires instance-level identification and the instance is not specified, you will see an error in the validation report. To resolve this error, use an instance-level overlay and be more explicit in the overlay file as to which instance should be overlaid. For more information, see Overlayable fields.