I tried to figure out what use Sun was to ORACLE. After all, they were mostly famous for Java and Open Office, which were being given away. And Solaris was a "real UNIX", but how valuable is that when Linux is being given away?
My conclusion was that Oracle, in competing head-on with IBM and its DB/2 database product, felt it needed to level the playing field by being a hardware company instead of a software company. At the time, SPARC processors from Sun had RAS features, just as IBM mainframes do, and just as Itanium chips from Intel did... but which were conspicuously absent from the x86 platform.
So, given that the future of the Itanium was doubtful, instead of simply making Oracle-branded Itanium boxes, Oracle decided that buying Sun was the simplest way to get a stable supply, because they would control it, of processors with RAS (Reliability, Availability, Serviceability - in the IBM version of the acronym; Sun has the S stand for Scaleability instead).
Shortly after, Intel came out with the Nehalem-EX, bringing RAS to the x86 platform. Oops.
Even with Intel's premium pricing on Xeons, Oracle would be hard pressed to match the price/performance of Intel chips, and so the value of the Sun acquisition to it seems to have largely evaporated when that happened.