DB2 and Oracle are known to be enterprise solutions. There was a time when Oracle was highly different from DB2, but probably because of the new releases of DB2, it has proven that it is not much different from Oracle anymore. The major difference is how transaction isolation can be achieved, but aside from that, it will just depend on people’s preferences, which one they would like to use more.
Oracle comes with a lot of features that will be compatible to be used in so many other things. Another difference is the limitation of character. Oracle still offers limited characters, which is about 30 characters. DB2 will offer limited characters for the username.