The move comes shortly after Salesforce.com announced Database.com, a pay-as-you-go product that is also powered in part by Oracle’s database. Like Amazon’s other cloud infrastructure offerings, the upcoming Oracle database service will feature hourly fees, with no long-term contract required.

Amazon already offered support for MySQL on the Relational Database Service. The addition of Oracle will give those users the same benefits of reduced database administration efforts and elastic scalability of the underlying storage and computing resources, Amazon said.

Hourly pricing, which wasn’t disclosed Tuesday, will depend on the Oracle database edition and instance size, Amazon said.

Amazon will also be offering reserved database instances, in which customers pay a one-time fee “and in turn receive the option to run that DB Instance at a significant discount on the ongoing hourly usage charge.”

The cost of the service will no doubt be closely watched. Salesforce.com is offering a basic version of Database.com at no charge, with costs added based on the number of records, transactions and users, as well as optional enterprise services for identity management, authentication and security.

The announcement builds on Oracle and Amazon’s existing relationship, which has already enabled users to run Oracle middleware, database software and applications on the AWS cloud.