code: public final synchronized long nextId(Object obj)
  	{
  		if (tc.isEntryEnabled()) Tr.entry(tc, "nextId", obj);
  		
  		long id = _idCount++;
  
  		// Keep incrementing the id until we
  		// find one that hasn't been reserved.
  		while (_idMap.get(id) != null)
  		{
  			id = _idCount++;
  		}
  
  		// Add the new id to the map associating
  		// it with the given object.
  		_idMap.put(id, obj);
  
  		if (tc.isEntryEnabled()) Tr.exit(tc, "nextId", new Long(id));
  
  		return id;
  	}
docs: Returns the next available id, starting from 1, and associates
  it with the given object. This method should be used during
  the creation of a new recoverable object.
  
  @param obj The object to be associated with the id
  
  @return The next available recoverable unit id