code: public final synchronized void incrementReferenceCount() throws SevereMessageStoreException
      {
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) SibTr.entry(this, tc, "incrementReferenceCount");
  
          if (_referenceCountIsDecreasing)
          {
          	if (TraceComponent.isAnyTracingEnabled() && tc.isEventEnabled()) SibTr.event(this, tc, "Cannot increment! Reference count has begun decreasing.");
          	if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) SibTr.exit(this, tc, "incrementReferenceCount");
              throw new SevereMessageStoreException("Cannot add more references to an item after one has been removed");
          }
          _referenceCount++;
  
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) SibTr.exit(this, tc, "incrementReferenceCount");
      }
docs: This method is called when a reference is being added by an active transaction
  and when a reference is being restored.
  It should only be called by the message store code.
  @throws SevereMessageStoreException