private void syncDbRecordsMergeFailure() {
   DiskImage curr = getDestinationDiskImage();
   while (!curr.getImageId().equals(getDiskImage().getImageId())) {
     curr = getDbFacade().getDiskImageDao().getSnapshotById(curr.getParentId());
     getImageDao().updateStatus(curr.getImageId(), ImageStatus.ILLEGAL);
   }
 }
 // function return the index of the image that has no parent
 private static int getFirstImage(List<DiskImage> images, DiskImage curr) {
   for (int i = 0; i < images.size(); i++) {
     if (curr.getParentId().equals(images.get(i).getImageId())) {
       return i;
     }
   }
   return -1;
 }
  /**
   * After merging the snapshots, update the image and snapshot records in the database to reflect
   * the changes. This handles either forward or backwards merge (detected). It will either then
   * remove the images, or mark them illegal (to handle the case where image deletion failed).
   *
   * @param removeImages Remove the images from the database, or if false, only mark them illegal
   */
  private void syncDbRecords(boolean removeImages) {
    // If deletion failed after a backwards merge, the snapshots' images need to be swapped
    // as they would upon success.  Instead of removing them, mark them illegal.
    DiskImage baseImage = getDiskImage();
    DiskImage topImage = getDestinationDiskImage();

    // The vdsm merge verb may decide to perform a forward or backward merge.
    if (topImage == null) {
      log.debug("No merge destination image, not updating image/snapshot association");
    } else if (getParameters().getMergeStatusReturnValue().getBlockJobType()
        == VmBlockJobType.PULL) {
      // For forward merge, the volume format and type may change.
      topImage.setvolumeFormat(baseImage.getVolumeFormat());
      topImage.setVolumeType(baseImage.getVolumeType());
      topImage.setParentId(baseImage.getParentId());
      topImage.setImageStatus(ImageStatus.OK);

      getBaseDiskDao().update(topImage);
      getImageDao().update(topImage.getImage());
      updateDiskImageDynamic(topImage);

      updateVmConfigurationForImageRemoval(
          baseImage.getImage().getSnapshotId(), baseImage.getImageId());
    } else {
      // For backwards merge, the prior base image now has the data associated with the newer
      // snapshot we want to keep.  Re-associate this older image with the newer snapshot.
      // The base snapshot is deleted if everything went well.  In case it's not deleted, we
      // hijack it to preserve a link to the broken image.  This makes the image discoverable
      // so that we can retry the deletion later, yet doesn't corrupt the VM image chain.
      List<DiskImage> children =
          DbFacade.getInstance().getDiskImageDao().getAllSnapshotsForParent(topImage.getImageId());
      if (!children.isEmpty()) {
        DiskImage childImage = children.get(0);
        childImage.setParentId(baseImage.getImageId());
        getImageDao().update(childImage.getImage());
      }

      Image oldTopImage = topImage.getImage();
      topImage.setImage(baseImage.getImage());
      baseImage.setImage(oldTopImage);

      Guid oldTopSnapshotId = topImage.getImage().getSnapshotId();
      topImage.getImage().setSnapshotId(baseImage.getImage().getSnapshotId());
      baseImage.getImage().setSnapshotId(oldTopSnapshotId);

      boolean oldTopIsActive = topImage.getImage().isActive();
      topImage.getImage().setActive(baseImage.getImage().isActive());
      VolumeClassification baseImageVolumeClassification =
          VolumeClassification.getVolumeClassificationByActiveFlag(baseImage.getImage().isActive());
      topImage.getImage().setVolumeClassification(baseImageVolumeClassification);
      baseImage.getImage().setActive(oldTopIsActive);
      VolumeClassification oldTopVolumeClassification =
          VolumeClassification.getVolumeClassificationByActiveFlag(oldTopIsActive);
      topImage.getImage().setVolumeClassification(oldTopVolumeClassification);

      topImage.setSize(baseImage.getSize());
      topImage.setImageStatus(ImageStatus.OK);
      getBaseDiskDao().update(topImage);
      getImageDao().update(topImage.getImage());
      updateDiskImageDynamic(topImage);

      getBaseDiskDao().update(baseImage);
      getImageDao().update(baseImage.getImage());

      updateVmConfigurationForImageChange(
          topImage.getImage().getSnapshotId(), baseImage.getImageId(), topImage);
      updateVmConfigurationForImageRemoval(
          baseImage.getImage().getSnapshotId(), topImage.getImageId());
    }

    Set<Guid> imagesToUpdate = getParameters().getMergeStatusReturnValue().getImagesToRemove();
    if (imagesToUpdate == null) {
      log.error("Failed to update orphaned images in db: image list could not be retrieved");
      return;
    }
    for (Guid imageId : imagesToUpdate) {
      if (removeImages) {
        getImageDao().remove(imageId);
      } else {
        // The (illegal && no-parent && no-children) status indicates an orphaned image.
        Image image = getImageDao().get(imageId);
        image.setStatus(ImageStatus.ILLEGAL);
        image.setParentId(Guid.Empty);
        getImageDao().update(image);
      }
    }
  }