eZ\Publish\Core\Repository\Repository::rollback PHP Method

    public function rollback()
    {
        try {
            $this->persistenceHandler->rollback();
            --$this->transactionDepth;
            unset($this->commitEventsQueue[$this->transactionCount]);
        } catch (Exception $e) {
            throw new RuntimeException($e->getMessage(), 0, $e);
        }
    }

 /**
  * Removes a relation of type COMMON from a draft.
  *
  * @throws \eZ\Publish\API\Repository\Exceptions\UnauthorizedException if the user is not allowed edit this version
  * @throws \eZ\Publish\API\Repository\Exceptions\BadStateException if the version is not a draft
  * @throws \eZ\Publish\API\Repository\Exceptions\InvalidArgumentException if there is no relation of type COMMON for the given destination
  *
  * @param \eZ\Publish\API\Repository\Values\Content\VersionInfo $sourceVersion
  * @param \eZ\Publish\API\Repository\Values\Content\ContentInfo $destinationContent
  */
 public function deleteRelation(APIVersionInfo $sourceVersion, ContentInfo $destinationContent)
 {
     $sourceVersion = $this->loadVersionInfoById($sourceVersion->contentInfo->id, $sourceVersion->versionNo);
     if ($sourceVersion->status !== APIVersionInfo::STATUS_DRAFT) {
         throw new BadStateException('$sourceVersion', 'Relations of type common can only be removed from versions of status draft');
     }
     if (!$this->repository->canUser('content', 'edit', $sourceVersion)) {
         throw new UnauthorizedException('content', 'edit', array('contentId' => $sourceVersion->contentInfo->id));
     }
     $spiRelations = $this->persistenceHandler->contentHandler()->loadRelations($sourceVersion->getContentInfo()->id, $sourceVersion->versionNo, APIRelation::COMMON);
     if (empty($spiRelations)) {
         throw new InvalidArgumentException('$sourceVersion', 'There are no relations of type COMMON for the given destination');
     }
     // there should be only one relation of type COMMON for each destination,
     // but in case there were ever more then one, we will remove them all
     // @todo: alternatively, throw BadStateException?
     $this->repository->beginTransaction();
     try {
         foreach ($spiRelations as $spiRelation) {
             if ($spiRelation->destinationContentId == $destinationContent->id) {
                 $this->persistenceHandler->contentHandler()->removeRelation($spiRelation->id, APIRelation::COMMON);
             }
         }
         $this->repository->commit();
     } catch (Exception $e) {
         $this->repository->rollback();
         throw $e;
     }
 }