Global transactions

If an application uses two or more resources, an external transaction manager is needed to coordinate the updates to all the resource managers in a global transaction.

Global transaction support is available to web and enterprise bean components and, with some limitations, to application client components. Enterprise bean components can be subdivided into two categories: beans that use container-managed transactions (CMT) and beans that use bean-managed transactions (BMT).

Only BMT enterprise beans, application client components, and web components can use the Java Transaction API (JTA) UserTransaction interface to define the demarcation of a global transaction. To obtain the UserTransaction interface, use a JNDI lookup of java:comp/UserTransaction, or use the getUserTransaction method from the SessionContext object.

The UserTransaction interface is not available to CMT enterprise beans. If CMT enterprise beans attempt to obtain this interface, an exception is thrown, in accordance with the EJB specification.

Ensure that programs that perform a JNDI lookup of the UserTransaction interface use an InitialContext that resolves to a local implementation of the interface. Also ensure that such programs use a JNDI location that is appropriate for the EJB version.

WebSphere Application Server Version 4 and later releases bind the UserTransaction interface at the JNDI location specified in the EJB Version 1.1 specification. This location is java:comp/UserTransaction.

A web component or enterprise bean (CMT or BMT) can use additional interfaces that provide JTA support. These interfaces provide the transaction identity and a mechanism to receive notification of transaction completion. The interfaces include the TransactionSynchronizationRegistry interface, the ExtendedJTATransaction interface, and the UOWSynchronizationRegistry interface.

Related concepts

JTA support

Local transaction containment

Client support for transactions