My advice is to forget DB2, it's certainly "solid" but let's say it's not the most used database for ARS so perhaps Support will have less experience compared to Oracle and SQL Server.
Believe me, I worked 18 months on a project using 7.6.04 and DB2 and it took some time to get all options right for DB2, especially view handling which is... Peculiar to say the least in DB2
But if you have a good DB2 DBA it's another story.
Other problem with DB2 is that some tools aren't compatible with it, let's say Analytics. So this could be also a problem if you have a replicated database and you want analytics on it.
Then again it'll depend on your database size, SQL Server "could" have problems if it's too big. May I ask why you're moving from Oracle? Too expensive?
I am currently working with a client using Solaris/Sybase. They are on 7.6.04 SP3, and they have been running Solaris/Sybase since version 2.0.
Sybase has the same nice Case Insensitivity settings as SQL-Server.
They recently investigated moving to Oracle, but the annual support cost was actually about 100 times (!!!) more expensive than Sybase. Maybe they have an old deal with Sybase, I don't know...
Best Regards - Misi, RRR AB, http://rrr.se
Totally understand looking at costs of support for various products; and I have no particular preference for which database you use; but I just want to put a plug in for including "training" as part of the cost of switching databases... if you have a lot of people who know Oracle and no one who knows SQL Server or Sybase or DB2, please include some training for a few of them on the new database s/w!
I'm sure you've already thought of this, just mentioning for others who might be contemplating a switch...