The docs (http://www.hibernate.org/hib_docs/v3/reference/en/html/session-configuration.html#configuration-optional) says that default value for hibernate.connection.release_mode is "on_close".
But in the source code (3.2.0.cr3) we can see, the default is "auto", which is either "after_transaction" or "after_statement" depending on the TransactionFactory.
See: org.hibernate.cfg.SettingsFactory line 168, org.hibernate.transaction.JDBCTransactionFactory line 19, org.hibernate.transaction.JTATransactionFactory line 61.
See also issue #HHH-1038
Either the docs or defaults should be changed.
make sure you are looking at documentation matching the version you are using