code: public long getUniqueValue() throws PersistenceException
      {
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) SibTr.entry(tc, "getUniqueValue");
  
          long retval;
              
          synchronized (_globalUniqueLock) 
          {
              if (_globalUnique == _globalUniqueThreshold) 
              {
                  _globalUniqueManager.scheduleUpdate(this);
              }
              else if (_globalUnique == _globalUniqueLimit) 
              {
                  _globalUniqueManager.updateEntry(this);
                  nextRangeMaximumAvailable();
              }
              
              retval = _globalUnique++;
          }
  
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) SibTr.exit(tc, "getUniqueValue", "return="+retval);
          return retval;
      }
docs: Returns a unique numeric value across the entire life of the message store.
  At least until the <code>long</code> value wraps around.
  
  @return a value which is unique across the entire life of the
  message store