Cannot open connection Error on large hibernate updates/inserts

Problem:Recently I was getting "Cannot open connection/Transaction Inactive" Error when doing  large number (100000) updates with hibernate
Session session = sessionFactory.openSession();
Transaction tx = session.beginTransaction();
for ( int i=0; i<;100000; i++ ) {
       Customer customer = new Customer(.....);
       session.save(customer);
}
tx.commit();
session.close();
Solution:When making new objects persistent flush() and then clear() the session regularly in order to control the size of the first-level cache.

Session session = sessionFactory.openSession(); 
Transaction tx = session.beginTransaction(); 
for ( int i=0; i<;100000; i++ ) { 
 Customer customer = new Customer(.....); 
 session.save(customer); 
 if ( i % 20 == 0 ) { //similar to JDBC batch 
 //flush a batch of inserts and release memory:
 session.flush(); 
 session.clear(); 
 } 
} 
tx.commit();
session.close();