Fal::deleteSysFileReference() 

public function deleteSysFileReference( $uidOrFileReference = null )
{
	$uid = null;
	if (is_a($uidOrFileReference, \TYPO3\CMS\Extbase\Domain\Model\FileReference::class )) {
		$uid = $uidOrFileReference->getUid();
	} else if (is_numeric($uidOrFileReference)) {
		$uid = $uidOrFileReference;
	}
	if ($uid) {
		// ToDo: Ab Typo3 v10 prüfen, ob delete() implementiert wurde
		/*
		$resourceFactory = \nn\t3::injectClass( \TYPO3\CMS\Core\Resource\ResourceFactory::class );
		$fileReferenceObject = $resourceFactory->getFileReferenceObject( $uid );
		$fileReferenceObject->delete();
		*/
		// ToDo: Ab Typo3 v8 prüfen, ob das hier nicht einfacher wäre:
		/*
		$fal = $this->persistenceManager->getObjectByIdentifier($uid, \TYPO3\CMS\Extbase\Domain\Model\FileReference::class, false);
		$this->persistenceManager->remove( $fal );
		*/
		\nn\t3::Db()->delete('sys_file_reference', $uid);
	}
}