Good Question

When a change in Requirement happend
first we need to identify the affected testcases then we 
need to modify or edit or block the existing test case. 

Very first time after preparation of test cases we used to 
update the Traceability matrix.

Traceabnility Matrix maps Requirements to Testcase.
In this matrix 
For every Requirement ID mapped with the prepared test case 
ID.

When a perticular requirement changed then we will look 
the traceability matrix to identify the coressponding 
testcase ID's.

According to the change in requirement we need to change 
the corresponding testcase.

The the traceability matrix again should update for future 
reference.

Ok Friends 

byee

Rajendra Prasad Reddy
+919885162742
hyderabad
India

to creat a new test case.

Nice explaination Rajendra...

Thanka
Sumiksha