To use web service source and target definitions in a staged mapping, you must include a message ID in the web source and target definitions. The Web Services Hub uses a message ID as a primary key to bind the requests and responses for a web service. For example, the first session reads from a web service source and writing to a relational target. The second session uses the relational target as a source and writes to a web service target. The Web Services Hub uses the message ID to associate the input message of the request in the first session to the output message in the response of the second session.

You must also include a message ID in the web source and target definitions when you run a web service session on a grid. When you run a web service session on a grid, the Integration Service distributes session threads to multiple DTM processes on nodes in the grid. The Integration Service uses the message ID to associate the web service input and output messages across the nodes.

If you add the message ports when you create a web service source or target definition, the Designer adds message ID and client ports to the envelope view.

The following table describes the message ID and client ports added to the envelope view: