s3BackupMode

Specifies how you want Firehose to back up documents to Amazon S3. When set to FailedDocumentsOnly, Firehose writes any data that could not be indexed to the configured Amazon S3 destination. When set to AllEvents, Firehose delivers all incoming records to Amazon S3, and also writes failed documents to Amazon S3. The default value is FailedEventsOnly.

You can update this backup mode from FailedEventsOnly to AllEvents. You can't update it from AllEvents to FailedEventsOnly.