The fund's commodity exposure is leveraged trough purchases of derivatives (options, futures, etc.). Therefore, the fund holds a large amount of cash reserves. It parks that money in inflation protected government investments and other corporate debentures, which show up as the largest holdings.
"PIMCO's CommodityRealReturn Strategy seeks to match the Dow Jones AIG Commodity Index. The DJ-AIG Commodity Index reflects changes in a broad range of commodity futures prices, from crude oil and coffee to gold and cattle."