Oracle Corp.’s most high-profile medical records customer, the US Department of Veterans Affairs, says the company’s software is failing at its main job of helping improve patient care, according to previously unpublished internal survey data.The VA has been renegotiating its $16 billion contract with Oracle due to poor performance of the system and employee feedback. The department is Oracle’s top public client in its health unit, which includes Cerner, the electronic medical records provider p...