The DataSource implementation in the Application Server provides a getNonTxConnection method, which retrieves a JDBC connection that is not in the scope of any transaction. There are two variants, as follows:
public java.sql.Connection getNonTxConnection() throws java.sql.SQLException
public java.sql.Connection getNonTxConnection(String user, String password) throws java.sql.SQLException
Another way to get a non-transactional connection is to create a resource with the JNDI name ending in __nontx. This forces all connections looked up using this resource to be non transactional.
Typically, a connection is enlisted in the context of the transaction in which a getConnection call is invoked. However, a non-transactional connection is not enlisted in a transaction context even if a transaction is in progress.
The main advantage of using non-transactional connections is that the overhead incurred in enlisting and delisting connections in transaction contexts is avoided. However, use such connections carefully. For example, if a non-transactional connection is used to query the database while a transaction is in progress that modifies the database, the query retrieves the unmodified data in the database. This is because the in-progress transaction hasn’t committed. For another example, if a non-transactional connection modifies the database and a transaction that is running simultaneously rolls back, the changes made by the non-transactional connection are not rolled back.
Here is a typical use case for a non-transactional connection: a component that is updating a database in a transaction context spanning over several iterations of a loop can refresh cached data by using a non-transactional connection to read data before the transaction commits.