The master thread creates a reader and transformation thread for each pipeline in the target load order group. A target load order group has multiple pipelines when it contains a transformation with multiple input groups.
When you connect more than one pipeline to a multiple input group transformation, the Integration Service maintains the transformation threads or creates a new transformation thread depending on whether or not the multiple input group transformation is a partition point:
Partition point does not exist at multiple input group transformation.
When a partition point does not exist at a multiple input group transformation, the Integration Service processes one thread at a time for the multiple input group transformation and all downstream transformations in the stage.
Partition point exists at multiple input group transformation.
When a partition point exists at a multiple input group transformation, the Integration Service creates a new pipeline stage and processes the stage with one thread for each partition. The Integration Service creates one transformation thread for each partition regardless of the number of output groups the transformation contains.