Users of IBM's System i hardware line will be able to run the MySQL open source database on the midrange servers, the two companies have announced.

The System i version of IBM's DB2 database, which is integrated with the midrange line's operating system as a standard feature, will serve as a certified storage engine for MySQL, the two firms said at MySQL's annual user conference in California.

MySQL claims that its database is being used in 11m active installations worldwide. The software is based on a modular architecture that lets users swap in different storage engines tuned for different application scenarios.

Companies that use the System i - better known by its original AS/400 name, and then as the iSeries - will gain the advantage of being able to implement online and transactional MySQL applications while continuing to store data in DB2, according to the two vendors.

The agreement to combine the technologies "is about opening up new applications to old data and old applications to new data," said Mike Smith, IBM's chief software architect for the System i line.

"I think it's an interesting and potentially excellent deal for both sides," said Stephen O'Grady, an analyst at the consulting firm RedMonk. "IBM gets access to the more or less ubiquitous MySQL platform with its DB2 storage engine, and MySQL gets an opening to the still popular [System i] platform."

DB2 is one of the three leading relational databases used by large enterprises, along with Oracle and Microsoft's SQL Server. But MySQL's low cost of ownership and rapid rise in popularity has led to the creation of a larger ecosystem of supporting software for the open source database than is currently available for DB2.

In addition, MySQL is making inroads into the installed bases of the top database vendors. For example, one-third of the 269 Oracle users who responded to an email survey conducted last June for the Independent Oracle Users Group said that they also use MySQL.

IBM also agreed to sell service and support subscriptions for the MySQL Enterprise database via its reseller network and the System i sales team. That should help MySQL, which is preparing for an initial public offering, to gain more paying customers. During his keynote speech, MySQL chief executive officer Marten Mickos said that his company has just one paying user for every thousand nonpaying ones.

In another effort to increase its count of paying customers, MySQL in January announced a site licence that lets companies deploy as many MySQL databases as they want for a flat fee of $40,000 (£20,000) per year. That price, Mickos claimed, is roughly comparable to the cost of one single-processor Oracle server licence.

The MySQL Enterprise Unlimited offering has attracted users such as ESPN, The New York Times and TransUnion, according to MySQL. Mickos said that in this year's first quarter, the company doubled the number of MySQL Enterprise subscriptions sold compared with the same period last year.

MySQL recently also updated a remote network monitoring service, rolled out last autumn, that can scan all of the database servers behind a customer's firewall, check to see if they are set up correctly and then provide advice on how to make them adhere to best practices.

Mickos said that can "take away the black-box feel that servers sometimes have and help you implicate or exonerate the database when an application is not running well."