As we all known, IBM and Oracle are close rivals in database industry for the past few years. Last year, IBM and Oracle tied for No. 1 in worldwide new license sales for relational database management systems, as the total market rose more than 10 percent to $7.8 billion, a market research firm said.

The difference in revenues between the two companies was less than $30 million, making it too close to statistically identify who is the leader of relational database market, Gartner Inc. said.

Quoted:
Based on the small amount separating the two companies, IBM had 34.1 percent of the market and Oracle 33.7 percent, or $2.665.9 billion and $2.636 billion, respectively. Microsoft was third with 20 percent, or $1.6 billion. NCR Teradata and Sybase were fourth and fifth, respectively, 2.9 percent and 2.3 percent of the market.

[Source]