* U.S. stocks up in early trading
* BOJ targets long-term yields
* Oil prices jump after EIA data (Updates with early U.S. market activity, changes dateline, previous LONDON)
By Caroline Valetkevitch
NEW YORK, Sept 21 (Reuters) - Global stock indexes rose and the dollar fell to its lowest against the yen in nearly a month on Wednesday after the Bank of Japan overhauled its monetary policy to target interest rates and ahead of a Federal Reserve decision later in the day.
With the global economy showing few signs of rebounding and investors fretting about the limits of monetary easing by major central banks, the BOJ's move came mostly as a welcome relief for markets.
The BOJ maintained its 0.1 percent negative interest rate, but abandoned its base money target. Instead, it set a "yield curve control" under which it will buy long-term government bonds to keep 10-year bond yields around their current zero percent. Fed will announce its policy decision at 2 p.m. EST (1800 GMT). Expectations of a rate increase have all but evaporated, but investors will comb the U.S. central bank's statement for clues about whether it will hike in coming months.
"The BOJ made some dovish comments and that has given investors an early push on the likelihood of no action from the Fed," said Andre Bakhos, managing director at Janlyn Capital in Bernardsville, New Jersey.
The Fed raised rates for the first time in nearly a decade in December but weak economic data and global uncertainty have prevented further rate increases.
Oil prices jumped and the S&P energy index .SPNY rose 1.2 percent, leading gains in the S&P 500.
The Dow Jones industrial average .DJI was up 56.67 points, or 0.31 percent, to 18,186.63, the S&P 500 .SPX gained 7.96 points, or 0.37 percent, to 2,147.72 and the Nasdaq Composite .IXIC added 19.90 points, or 0.38 percent, to 5,261.25.
MSCI's all-country world stock index .MIWD00000PUS was up 0.7 percent, while Europe's STOXX 600 .STOXX rose 0.5 percent, helped by euro zone banking shares.
The dollar fell more than 1 percent against the yen to 100.56 yen JPY= in early North American trading, its lowest since Aug. 26.
In the bond market, U.S. Treasury yields rose ahead of the Fed decision. The yields initially climbed on selling in bond markets worldwide following the BOJ policy reboot.
"If the Fed doesn't move today ... the market will shift its focus to December. December is their last chance to move this year," said Brian Edmonds, head of rates trading at Cantor Fitzgerald in New York.
In commodities, oil prices extended gains after data showed U.S. crude stocks fell sharply last week. O/R
U.S. crude futures CLc1 jumped 2.5 percent to $45.12 a barrel, while Brent crude futures LCOc1 were up 1.8 percent at $46.72.