In Tamil Nadu there is no launch of 3g in tata docomo but you can get 3g speed.
Just Follow the steps below:
Step1: DIAL *141*1#
Step2: Now it will ask to select the state tamil nadu but not available so select KERALA
Step3: Choose a plan which is little higher than your balance and proceed, it will send a message to you that this facilities is not available in your area.
Step4: Now recharge Gprs pack of Rs.5 and check out the speed.
You will be Shocked!!!!!!!!
This Works because when your select kerala state the system thinks that you are in kerala and immediately gives the access of 3g speed to your no and you receive a message of no 3g in your area after giving you access of 3g and doesn't take away the access of 3g speed back. I and my friends personally tested in tamil nadu. I hope this trick also works in other states just check it out and share your results. In Place of kerala select your nearest state which is already enabled 3g in docomo.
Don't forget to say thanks.....