docs: public final ItemReference findOldestReference() throws MessageStoreException
      {
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
              SibTr.entry(this, tc, "findOldestReference");
  
          ReferenceCollection ic = ((ReferenceCollection) _getMembership());
          if (null == ic)
          {
              if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
                  SibTr.exit(this, tc, "findOldestReference");
              throw new NotInMessageStore();
          }
          ItemReference item = null;
          if (ic != null)
          {
              item = (ItemReference) ic.findOldestItem();
          }
  
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
              SibTr.exit(this, tc, "findOldestReference", item);
          return item;
      }