code: private void acknowledgeAlreadyProcessedOperation(SegmentOperation operation) throws DataCorruptionException {
          if (operation instanceof MergeSegmentOperation) {
              // Only MergeSegmentOperations need special handling. Others, such as StreamSegmentSealOperation, are not
              // needed since they're handled in the initialize() method. Ensure that the DataSource is aware of this
              // (since after recovery, it may not know that a merge has been properly completed).
              MergeSegmentOperation mergeOp = (MergeSegmentOperation) operation;
              try {
                  updateMetadataForTransactionPostMerger(this.dataSource.getStreamSegmentMetadata(mergeOp.getSourceSegmentId()), mergeOp.getStreamSegmentId());
              } catch (Throwable ex) {
                  // Something really weird must have happened if we ended up in here. To prevent any (further) damage, we need
                  // to stop the Segment Container right away.
                  throw new DataCorruptionException(String.format("Unable to acknowledge already processed operation '%s'.", operation), ex);
              }
          }
      }
docs: Processes (acks) an operation that has already been processed and would otherwise result in no change to the
  underlying Storage.
  
  @param operation The operation to handle.