When performing a search, you might see 0 showing for the AvailableRooms node in the search response.
This field shows you the maximum number of rooms that are available to book. Only rooms with availability are returned, therefore a value of 0 is equivalent to no max cap / unlimited.
Also, whether this value shows a number of rooms >0 will very much depend on whether the supplier returning availability supports this field, and whether iVectorOne has integrated against it