RE: Yes you are missing something...
".......It is easy to move an Oracle DB from one platform to another....." It's also quite easy to export a database from Oracle and transfer it to DB2 or Sybase, there are tools and services from hp and IBM for just such moves.
Despite their non-to-hidden rivalry with hp, IBM are not stupid and keep DB2, Informix and WebSphere products humming on hp-ux, beacuse they know they will sell more software than just offering it on Pee-series alone. And Sybase is now a SAP product, a company that already has a good relationship with hp (and a big reason to hurt Oracle). And that's before you consider ideas like ProgreSQL, or Intersystems Cache for OpenVMS.
".....It's that Oracle DB which basically dictates the entire Unix market....." There are two really dominant databases - M$ SQL Server and Oracle's - and they rose to dominance by being multi-platform, having good perfromance, and good support. For many years, M$ SQL Server has been out-selling Oracle, just as Windows and Linux have been eating into the UNIX base. Larry's response has been a desperate retreat to a walled garden to preserve his profit margins, but in doing so he is removing the multi-pltaform choice that made Oracle software attractive. His plan seems to be to eventually restrict his software to hardware only wearing an Oracle badge (e.g., Exedata). Which is not attractive to us customers that value choice. In short, he has now made DB2 and Sybase more attractive.