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External syncpoint coordination

 

A global unit of work can also be coordinated by an external X/Open XA-compliant transaction manager. Here the WebSphere MQ queue manager participates in, but does not coordinate, the unit of work.

The flow of control in a global unit of work coordinated by an external transaction manager is as follows:

  1. An application tells the external syncpoint coordinator (for example, TXSeries) that it wants to start a transaction.

  2. The syncpoint coordinator tells known resource managers, such as WebSphere MQ, about the current transaction.

  3. The application issues calls to resource managers associated with the current transaction. For example, the application could issue MQGET calls to WebSphere MQ.

  4. The application issues a commit or backout request to the external syncpoint coordinator.

  5. The syncpoint coordinator completes the transaction by issuing the appropriate calls to each resource manager, typically using two-phase commit protocols.

The supported levels of external syncpoint coordinators that can provide a two-phase commit process for transactions in which WebSphere MQ participates are defined at: http://www.ibm.com/support/docview.wss?rs=171&uid=swg27006467

See the WebSphere MQ Application Programming Guide for information about writing and building transactions to be coordinated by an external syncpoint coordinator.

The rest of this chapter describes how to enable external units of work.

 

Parent topic:

Scenario 2: Other software provides the coordination


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