Propelled by the continued migration of databases to Linux, Oracle extended its lead over IBM in the global market for relational databases last year, according to Gartner.

Gartner publicly released its database market numbers for 2006 this week, saying that worldwide sales totalled $15.2 billion (£7.7bn). Oracle had a 47.1% market share thanks to $7.2bn in database-related revenue, said Gartner.

Oracle's database revenue increased 14.9% year-to-year, and its market share ticked up from 46.8% in 2005, Gartner said.

The analyst gave second-place IBM 21.1% of the market, with relational database sales of $3.2 billion – up 8.8% from the sales level during 2005. But IBM's market share dropped from 22.1% in 2005, as its revenue increase fell short of the 14.2% growth of the market as a whole.

Microsoft remained in third place with a 17.4% market share last year, according to Gartner. But the firm said that Microsoft gained ground on IBM, thanks to year-over-year sales growth of 28% that bumped up its revenue total to $2.7bn.

NCR's Teradata division, which is being spun off into a separate company, and Sybase rounded out the list of the top five vendors during 2006. But Teradata and Sybase lagged far behind the three leaders, with Gartner giving each a 3.2% market share.

"Organisations are looking to gain insight into the business to make better decisions and identify new opportunities," Gartner analyst Colleen Graham said. "This is forcing them to invest in their data assets, purchase new technology and tools that increase operational efficiency and enable better use of data management resources."

Gartner's figures include new licence fees and revenue from updates, subscriptions and hosting as well as technical support and maintenance costs. The numbers exclude professional services and hardware revenue.

According to Gartner, Unix and Windows continued to be the most popular operating systems for relational databases, accounting for 34.8% and 34.5% of the market, respectively. Linux remained in third place with 15.5% of the market, although Linux-based revenue jumped 67% from its 2005 level.

Each of the three major vendors again dominated the particular operating system platforms that it is best known for, Gartner said. That includes Oracle on Unix and Linux, Microsoft on Windows and IBM on the z/OS operating system for its zSeries servers.

Gartner's figures also echoed preliminary data released in April by rival market researcher IDC, which also said that Oracle extended its lead over IBM last year. Although IDC valued the market as being slightly larger than Gartner did, putting the overall revenue total at $16.5bn.