In June, HP took legal action against Oracle for failing to meet its commitments to the vendor and 140,000 shared customers by ending software development for HP's Itanium servers.
HP builds Integrity servers with the Itanium chip, which the company co-developed with Intel in the 1990s, until the chip giant took over all Itanium development from 2004.
Oracle's countersuit claims the Itanium partnership was an informal one and that Oracle had always retained the right to support whatever HP technologies it chose.
In announcing its decision to stop Itanium development in March, Oracle said Intel had made it clear Itanium was nearing the end of its life.
Oracle's claim was denied immediately by Intel chief executive Paul Otellini, who issued a statement that it continued to have an ambitious roadmap for Itanium.
At the time, Oracle said it could prove its claim in court, but in the countersuit has chosen to focus instead on invalidating an agreement between the two companies to extend their partnership.
The agreement was reached as part of a settlement of the dispute over Oracle's decision to hire Mark Hurd after he was ousted as head of HP over sexual harassment allegations.
HP said the agreement commits Oracle to continue support for Itanium, but in its countersuit, Oracle claims HP entered into the agreement in bad faith.
A version of this story first appeared on www.computerweekly.com