Best Hardware/Database Combo

The Hardware choices: HP-9000 and RS/6000 The Database choices: Informix, Sybase, Oracle The Application: typical business application - by day primarily OLTP, by night a batch animal The Situation: we have an in-house application currently running on a proprietary mini network (Wang). We've got about 400 users during normal business hours, in the neighborhood of 40-50 off-hours. The application comprises about 2.5 million lines of COBOL and C. We do not have a database. We're gonna move to Unix. The production environment includes 2 main CPU's and several smaller CPU's used mainly for connection the main CPU's. There is much data sharing across the CPU's. The work schedules of the primary users of each of the main CPU's is very different. In your experience, which hardware/database combination sounds like a best-fit for our situation? How well do the databases take advantage of the capabilities of the hardware? How much help do the tools provided (3rd-party ok) give in configuring the database? How's the support? There are lots of other questions I won't include here (the marketing reps are happy to answer them) but I'm interested in hearing how these products are working for you. Thank you for your advice and your comments, M. Livenspargar