Answer: Mandatory properties are enough to identify the object

Below i am giving the total process of object identification 

QTP uses three types of object identification to identify
the object

mandatory and assitive properties

smart identification 

and ordinal identifier

QTP starts with mandatory properties, if QTP unable to
identify the object uniquely using mandatory properties then
it will go to the assistive properties (if and only all
mandatory properties are matching with runtime object
properties)

(test object properties are the properties of objects in the
object repository and runtime object properties are
properties of the objects in the application)

if QTP unable to identify the object uniquely using
assistive properties then it will go to the smart
identification (we have to enable the smart identification
in object repository) (in smart identification the QTP
compares the object properties at the record or creat time
using base filter and optional filter properties) if any one
property matches then it will identifies the object.  

if QTP unable to identify the object uniquely using smart
identification then it will go to the ordinal identifier.

in ordinal identifier there are three options
INDEX:  Tab position (order of that object in that
application, eg: if there are three OK buttons, then it will
give the button value which is first in order is "0", second
button value is "1" and third button value is "2")

LOCATION: The value of object which is closed to x-axis
(using x and y coordinates) is "0", for second one "1", for
third one "2".

CREATION TIME: For brower we can use this (for each brower
it creates a time) using the time difference it will give
the value and identifies the object.  

if any queries plz mail me a.thirumalareddy@gmail.com