i booked a ticket to mumbai from chennai and i could have made a specific request for an upper berth ticket, whereas i  was allotted the middle berth. the disadvantage is that i could not sleep whenever i wanted to,and has to get the consent of the person occupying the lower berth before i put the middle berth for sleeping. another disadvantage is that the hot winds makes life miserable for the travellers wearing a thin white cotton cloth , whereas i was wearing a jeans pant and a thick cotton t-shirt.when i slept in the middle berth either on my back or on my sides, the portion of the body that is in touch with the rexin seats is wet due to sweating.to compound the matters the fan is running in the ceiling and helping to blow the hot air that is collected at the top back to the passengers who are travelling. a suggestion was said by a fellow co. passenger, as follows, when ever a train stops at a big junction arrangements can be made to spray water on top of the ceiling of the train compartments, then the compartment can get cooler due to evaporation of the water. it appeared to be a good suggestion to me. and can be tried at railway station where the water tanks in the latrines are refilled in major junctions.