The volatile Sensex at the Bombay Stock Exchange was 4 points up in the afternoon deals. The 30-share index, which rose 36 points in the previous trade, was trading 4 points in the positive territory at 20,105, when reports last came in.Meanwhile, the National Stock Exchange's index Nifty today breached 6,100 level after two years on the back of steady capital inflows amid strong corporate earnings. The wide-based Nifty rose by 19 points, to trade at 6,101 points in its opening session, a level not seen since January, 2011 . The 50-share index was also fluctuating in afternoon deals and was trading 2 points up to 6,084 a short while ago. Brokers said, steady inflow of capital inflows by foreign funds driven by the government's decision to de-regulate diesel prices in a key economic reform measure, and better-than-estimated third quarter earnings by some blue-chip companies, helped Nifty cross the 6,100-level.