Hibernate supports DB2 so that aspect should be OK without any changes (though you don't say which version of DB2 - DB2 390 is a very different beast). The only issue is your direct SQL. Typically, direct SQL is used in circumstances where the logic is too specialized to use Criteria or HQL so its probably going to be an issue. But assuming you've made judicious use of a DAO pattern it shouldn't be a massive job to work round.
Dinesh Ramakrishnan wrote:Can I know whats the issue with direct SQL's. We use direct SQL's mostly for read-only queries and I thought could modify the queries if for any Oracle specific keywords
This is the problem - that Oracle specific syntax creeps into hand coded queries. Like Oracle's rownum, vs db2's fetch first. Depending how many queries you have, this could be a lot of work to change.