Besides IBM and Microsoft, which each hold about a fifth of the database market, Oracle faces strong competition from Teradata Inc., Sybase Inc. and a whole ecosystem of innovative startups, noted Monash. "The DBMS industry isn't even the secure oligopoly it appeared to be earlier this decade," he wrote.

Oracle is also a non-factor in the smaller but still significant non-relational database market. According to IDC, Oracle held just 0.2% of the $3.34 billion market in 2007 through its database. Microsoft and IBM dominate that market with the desktop Access and mainframe IMS databases, respectively.

Gartner's Chin said that acquisition could prompt moves by Oracle that would prompt loud objections from the very-vocal MySQL customer base. For example, he said that Oracle could raise the price of enterprise subscriptions to MySQL, or require that customers purchase support from Oracle for all production MySQL databases, not just a few designated ones. "I would not be surprised if Oracle did that," he said.

Chin did note that Oracle did not meddle in the sales and marketing processes of open source databases BerkeleyDB and InnoDB after buying them in 2006 and 2005 respectively.

Also, Oracle has said early on that Sun will continue to operate as a separate entity. That means MySQL will likely at least maintain it independence, as well as staying far enough away from Oracle's pricey database to prevent inadvertent cannibalization, he said.