Global transaction and two-phase commit support process

For example, a Java EE-compliant application server such as WebSphere® Application Server communicates with the application components (for example, Java servlets or Enterprise JavaBeans components) and the resource managers (for example, IMS or DB2®) through the resource adapters (for example, the IMS TM resource adapter) to coordinate a transaction. If a transaction manager coordinates a transaction, that transaction is considered a global transaction. If a transaction manager coordinates a transaction with more than one resource manager, the external coordinator uses the two-phase commit protocol.

Suppose that you want to transfer money from your savings account to your checking account. If your savings account information resides on a separate resource manager from your checking account information (for example, your saving account resides on IMS and your checking account resides on DB2), the transaction manager in the application server (WebSphere Application Server) helps the application to coordinate the changes between IMS and DB2 transparently by using the two-phase commit processing. Specifically, the transaction manager works with the IMS TM resource adapter to coordinate the changes in IMS.

The IMS TM resource adapter is designed to work with the Java transaction manager in the Java EE platform, the Resource Recovery Services (RRS) of z/OS®, and IMS Connect to make consistent changes to IMS and other protected resources.

To participate in two-phase commit processing with IMS, the IMS TM resource adapter uses the IMS OTMA synchronization level sync-point protocol. To participate in global transaction and two-phase commit processing when the changes are requested from a remote application, IMS uses RRS on z/OS.

RRS acts as the external coordinator or sync-point manager to coordinate the update and recovery of resources. The IMS TM resource adapter and IMS Connect interact with the Java transaction manager running in the application server and RRS on z/OS to allow a global transaction running on a Java EE platform to participate in a coordinated update with IMS running on the host.