Saleforce.com will announce it's going into the online, database-as-a-service business Tuesday morning at its Dreamforce user group meeting in San Francisco. The move puts it on a collision course with another large applications and database vendor, Oracle, whose CEO, Larry Ellison, seemed to go out of his way to criticize Salesforce at his own user group meeting earlier this year.

Ironically, the cloud-based, elastic, highly available and multi-tenant Database.com service that Salesforce.com launches will be based on the Oracle database engine. Saleforce.com for 12 years has supplied its customer relationship management (CRM) application customers with database services powered by an underlying Oracle engine.

Salesforce chairman and CEO Marc Benioff said he would make the announcement during his Tuesday morning keynote address to the conference. About 20,000 attendees have registered for the largest Dreamforce user group staged to date.

"It's not like Database.com is going to be just Oracle," said Eric Stahl, senior director of product marketing, in an interview before the announcement. Oracle offers its database system as an individual or single company application through Amazon Web Services' EC2. But Stahl said a great deal of engineering effort was needed to build a set of multi-user database services on top of Oracle for it to become an online service, he said.

For example, Database.com will scale up or down as needed by its customers without human intervention. Hundreds or thousands of users will be concurrently making use of one Database.com set of services as opposed to Salesforce launching hundreds of instances of Oracle to meet demand. Such services would include database elasticity, replication, load balancing, backup, disaster recovery, high availability and automatic system upgrades.

"Our Database.com service is far more than just Oracle. All of our engineering is focused on our own multi-tenant system," he said.

Ellison explicitly challenged the reliability and security of multi-tenant systems when he urged 40,000 Oracle OpenWorld attendees Sept. 19 to adopt Oracle's applications and run them on Oracle's Exalogic Elastic Cloud hardware appliance, while dissing Salesforce's alternative. The Salesforce.com multi-tenant application was inherently vulnerable, he claimed. It has "a weak security model" and allows "the co-mingling of GE's data with Siemens' data" on the same server.

At the time, Salesforce.com spokesmen responded that Salesforce maintained the privacy and security of its customers' data on its own architecture. Stahl picked up the theme again: "Our database system supports two million users. We've supported 87,200 businesses" over the past 12 years, with high-level auditors from telecommunications, financial services and healthcare companies inspecting Salesforce.com's operations, Stahl reported.