code: public final void initialize() throws PersistenceException, SevereMessageStoreException
      {
          PersistentMessageStore pm = _messageStore.getPersistentMessageStore();
          final HashMap tupleMap = _buildTupleMap(pm);
          _buildStreamTree(tupleMap);
          _recoverStreamsWithInDoubts(pm);
      }
docs: This method essentially drives the initial loading of the cache layer from the
  persistence layer.
  @throws SevereMessageStoreException