Hi Narendra,
A few cents, under my opinion:
To find out the suitable field in Web service side,As my Functional people suggesting to go with unused fields which are there in XSD.
This is not so obvious like seems originally. Now you need only to add two fields, but if the changes increase with the time you will have an understable schemas with values in fields that they are not so enough descriptives.
But i can not blindly select two fields and map it. client is saying since WSDL maintained by XI u can change according to ur wish.
This is very logical, i think there is so much fear to make changes in the integrations systems, One reason to have a XI/PI is to reduce the costs and risks of interface changes.
This is very critical interface and WSDL is involving many XSD's internally and used this webservice for major interfaces.
This is an important risk point, from my point of view i like share between scenarios only schemas that their information is very clear and is difficult to have changes.
Here my queries:
1)if i want to change the webservice what i sud take care.
You should have a test case list. All the cases must be tested before and after. Try to put the fields under one tag with low cardinality zero avoiding interfere with the old tags, sometimes the business scenario prevent this altough you can analyse deeply if this aseveration is right. Always keep the old schema and the old mapping in case of an unexpected error in production enviroment, you will can revert as quick as possible.
2)what is the better approach for this?
It depends about the schemas, the new fields, if it is clear to put the data in generic fields, new changes expected in the future, etc.
From my point of view the PI should be a "live" tool and the changes dont be so dramatic. I prefer to share only typical information between scenarios, i usually think, if tomorrow need for example to add the fax number to the type person, will it neccesary to all scenarios?, may be yes, then person type must be share. This is not a perfect solution, you avoid to make tests in several scenarios with one little change, on the other side is quick way to work. You should think to maintain a leverage between approachs.
Regards and good luck.