Ask an Oracle Sales Guy/Gal!
Im not Sybase user as such , nor am I a Sales person, but the following make sense to me.
Why have some of your data on Sybase and some on Oracle.
I would imagine that is painful for a few reasons
a)You need both Sybase and Oracle dbas & developers.
b)You cant run neat queries between the two systems without lots of messing about. When your looking at Oracle data, your Sybase data may as well be on the moon and vice versa.
c)You have to own 2 licenses / support contracts.
d)Your data, processes, applications,.. are not one standard.
e)If you consolidate to one platform or database, you can have 1 operation to backup/failover/upgrade/.....
So why not migrate to Sybase?
This is an easy question. Oracle is way cooler.
I rest my case.
The list of Oracle features , products, services , tools and partners is seriously impressive.