How can i use hibernate when i have 2 database servers and in one transaction data is to be saved in 2 mapped tables that are in different databse servers. I have to rool back transaction in first server if transaction fails in second server.

In this case you have to setup two session factories, one for each database server. In addition to that you must configure 2 XA DataSources in your app server and you have to bind hibernate to JTA of your app server.

reffering to code below

Session session = HibernateUtil.getSessionFactory().getCurrentSession();

session.beginTransaction();

as in above code. the transaction in associated with one session, but my requirement is to attach one transaction with two sessions.

or is the case is that, using one session object i have access to both database servers??
like..
session.save(FirstPojo); // One DB server
session.save(secondPojo);// Other DB server

session.getTransaction().commit();
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in above case, is the commit is fired to both DB servers on successfull completion in both DB servers?

Call "UserTransaction.commit()" to commit JTA transaction.