It has had all the ingredients of an epic Silicon Valley collision between fierce rivals. Billions of dollars at stake. Powerful, high-profile executives at the epicenter. And accusations of technology theft that strike at the heart of the software industry's culture.

And, no, it is not the patent feud between smartphone competitors Apple and Samsung.

This seven-year legal war involves Oracle and SAP, the world's top two business software titans, which are set to square off again Tuesday in a federal appeals court in a case that riveted the valley when it went to trial in 2010. With $1 billion hanging in the balance, the outcome will decide whether a record judgment in a copyright infringement case holds up.