In order to accommodate more passengers, Indian Railway has got a system which is known as the system of Reservation Against Cancellation or RAC. This is nothing but to allow two passengers to share a single berth pending confirmation of berths mid way. The on board ticket checking staff after final checking, allot the vacant berths to the RAC passengers. They confirm berths on priority basis and non on first come first serve. The priority is ascertained not as per the RAC number written on the ticket but according to their position in a particular compartment.
The system is available in second class Sleeper, Three Tier AC and Second Class Ac. In sleeper and third Ac coaches Side Lower berths are used to accommodate two passengers. In sleeper class Six side lower berths are earmarked as RAC berths while in Ac 3Tier three side Lower berths are used for this purpose. In 2nd Ac two inside lower berths are used and are allotted to four passengers.
Before boarding a train, check your Wait listed tickets. In cell phone and computer the position is shown in a different way like RS 1 31 that suggests Rac in Sleeper 1 and the berth number is 31. Similarly, RSB1 23 is written, in case of Ac 3 tier Ticket and RSA1 37 in case of Ac 2 Tier ticket.
If a passenger does not want to travel in such position or without full confirm berth, he or she can ask for refund. A ticket placed in RAC is granted full refund. So make up your mind beforehand whether you want to make journey on such sharing position or not. If agreed you should keep in mind that your partner may be an old man or woman or an obese person. You should not feel awkward or uneasy sharing your berth. In Ac classes you will not be provided with Bed roll unless your RAC berth is confirmed. Practically, that does not happen but this is the rule and you should not create uneasy situation with the Ac attendants.
Indian railway ensures your hassle free journey and wants to provide you with full confirmed berths but that is subject to some conditions like availability of berths. So, don’t hackle on board staff.