Hibernate在查询大量数据时出错，说是内存溢出？怎么回事？

我查询少量数据时没问题，当查询上千条纪录时，出现一下错误：
net.sf.hibernate.impl.IteratorImpl next 严重: could not get next result
  java.lang.OutOfMemoryError rethrown as net.sf.hibernate.InstantiationException: Could not instantiate entity with CGLIB:
wanzitest1.Wanzi
这是什么错误啊！

加大jvm的内存或者

Iterator cats = sess.iterate("from eg.Cat as cat");; //a huge result set
while ( cats.hasNext(); ); {
    Cat cat = (Cat); iter.next();;
    doSomethingWithACat(cat);;
    sess.evict(cat);;
}