code: public boolean syncWaterMarks() {
          // Sync up low water marks
          for (String source : sourceWaterMarkMap.keySet()) {
              WaterMarkEntry wmEntry = sourceWaterMarkMap.get(source);
              wmEntry.setLWMScn(wmEntry.getHWMScn());
          }
          
          return flush();
      }
docs: Sync up low water marks to high water marks for all the sources.
  
  @return <tt>true</tt> if flush is successful.