Tracking rising global markets, the Sensex at the Bombay Stock Exchange gained 81 points, or 0.5 percent, to 17,563, today, as euro zone debt worries eased. The Nifty at the National Stock Exchange rose 18 points, or 0.4 percent, to 5,284.Stock markets in Japan, China, Hong Kong, South Korea and Singapore climbed between 0.8 percent and 3 percent, after Greece cancelled plans for a referendum on a financial bailout package.