@Kamesh Krishnamoorthy: Re# 141869-0
Upgradation is done when all passengers aren't being able to be accommodated in the train. It is free of cost. Upgradation is done upto two higher classes in the train (E.g. if the train doesn't have 3A, then SL passenger may be upgraded to 2A and even 1A) It is done at the time of charting. All passengers in a ticket are considered for upgradation together. CNF/RAC/WL passengers (all of them) are eligible for it, though some claim that WL passengers have got higher priority for Upgradation.