You can't cancel e-ticket after chart preparation. You need to file TDR before 30 mins from the departure of train. There are 2 scenarios for you.
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1) If you don't want to take risk of travelling in RAC, you can file TDR and take over the full berth. Also there is no 100% guarantee of refund, even TDR is filed on time. TDR is like lottery, depends on luck, onboard TTE and wait for 90 days.
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2) Cancel the non-travelling person ticket before chart-preparation and hope TTE can allot full berth to you. (very less chance seeing the status of sheshadri.
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Once i had brawl with TTE regarding TDR, he was not ready to mark another passenger as absent because " you have got full berth, so no need to mark as absent". I was hell bent and finally succeeded.