When using a JDO/JPA implementation such as JPOX in a normal Java environment (with no J2EE container), the Transactions are known as Locally Managed Transactions. The users code (or a framework such as Spring) will manage the transactions by starting, and commiting the transaction itself. With these transactions with JDO you would do something like

PersistenceManager pm = pmf.getPersistenceManager();
Transaction tx = pm.currentTransaction();
try
{
    tx.begin();
    
    {users code to persist objects}
    
    tx.commit();
}
finally
{
    if (tx.isActive())
    {
        tx.rollback();
    }
}
pm.close();

and with JPA

EntityManager em = emf.getEntityManager();
EntityTransaction tx = em.getTransaction();
try
{
    tx.begin();
    
    {users code to persist objects}
    
    tx.commit();
}
finally
{
    if (tx.isActive())
    {
        tx.rollback();
    }
}
em.close();

When you use a framework like Spring you would not need to specify the tx.begin(), tx.commit(), tx.rollback() since that would be done for you. The basic idea with Locally Managed transactions is that you are managing the transaction start and end.

When using a J2EE container you are giving over control of the transactions to the container. Here you have Container Managed Transactions. In terms of your code, you would do like the previous example except that you would OMIT the tx.begin(), tx.commit(), tx.rollback() since the J2EE container will be doing this for you.