At the stock markets, after a positive opening, the Sensex at the Bombay Stock Exchange gave up most of its initial gains, and climbed a marginal 6 points to 31,318, a short while ago.The Nifty at the National Stock Exchange was flat at 9,658.And at the foreign exchange market, the rupee weakened 3 paise to 64 rupees 46 paise against the dollar in afternoon deals.