Think of a train which has 100 reserved seats and 10 seats r for the RAC pax in that train. Now if already 110 people has reserved in that train and u r the 111th person to reserved in that train, then ur ticket will be in waiting list. Now suppose 1personout of those 110 before u has cancelled his ticket, then u ticket moves one position forward and u come within the 10 person who will have a RAC ticket. So u will now get a RAC ticket. Now suppose again 10 people out of those 109 peoples before u cancel their ticket in that train, so now u move forward by 10position and now u r among the 100 pax who will get a confirm seat.so now u will get a confirm ticket. If those cancellations don't occur then ur ticket will remain in RAC or WL as per...
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the availability.
The sequence of getting confirm ticket in a train with WL is
WL>>RAC>>confirm

@guest: Re# 91771-0
RAC= Reservation Against Cancellation
Different trains have different no. of RAC seats depending on the class of travel - SL/3A/2A. 1A and CC do not have RAC.
it will be approx.8 per coach in SL (figures may change) In 2A/3A it is less.
If...
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a passenger has RAC booking, he can travel in the train. The passenger will be sharing the Side Lower Berth with some other passenger.
Depending upon vacancy and sequence, RAC passengers are allotted berths during journey. it is also possible, that a passenger will have to travel in RAC witout getting full berth for the entire journey.

@guest: Re# 91771-0
RAC means Reservation Against Cancellation!
An RAC ticket gets you on the train (A WL ticket doesn’t) and in your chosen class, but there’s a chance you could end up with just a seat.
A berth is split into 2 seats for 2 RAC ticket holders, if there’s any last minute cancellations, or if any quota allocations remain unsold, or if...
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any confirmed ticket holders are given a free upgrade (more later), an RAC ticket holder is given the empty berth, the other RAC ticket holder can then convert the 2 seats into a berth.