docs: @Override
      public void setCompletedPrefix(long newPrefix)
      {
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
              SibTr.entry(this, tc, "setCompletedPrefix", Long.valueOf(newPrefix));
  
          // If the completedPrefix is updated then update the 
          // other control variables.
          //We synchronize to ensure the saftey
          synchronized (oststream) //defect 256036
          {
              if (oststream.setCompletedPrefix(newPrefix) == true)
              {
                  doubtHorizon = newPrefix + 1;
                  unknownHorizon = newPrefix;
  
                  if (TraceComponent.isAnyTracingEnabled() && tc.isDebugEnabled())
                      SibTr.debug(tc, "doubtHorizon:" + doubtHorizon + " unknownHorizon:" + unknownHorizon);
              }
          }
  
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
              SibTr.exit(tc, "setCompletedPrefix");
      }