Both IDC and Dataquest Inc. said Oracle had nearly half of the total market by revenue, which IDC valued at US$14.6 billion and Dataquest pegged as $13.8 billion. The markets basically remained an oligopoly, with both analyst firms showing IBM with about 22 percent of the market and Microsoft Corp., despite strong year-over-year gains from its release of SQL Server 2005, still in third place -- with 17 percent of the market, according to IDC, or 15 percent, according to Dataquest.

Despite the oft-cited maturity of the database market, sales still grew year over year by 8.3 percent, said Dataquest, which is a unit of Gartner Inc. IDC pegged the annual growth at 9.4 percent.

The two research firms use different methodologies to calculate market share, leading to slightly different figures for the same companies, as well as for their annual growth rates.

Linux was the fastest-growing database platform, up 84 percent year over year and "driven primarily by Oracle," according to Gartner analyst Colleen Graham. Database revenues on mainframes grew faster than database revenues on Unix.

NCR Corp.'s Teradata unit and Sybase Inc. rounded out the top five, with each company taking about 3 percent market share. The former saw growth due to strong interest in data warehousing, while the latter was boosted by strong sales in Asia, especially China, according to IDC.