When you run a session on a grid, the Data Transformation Manager process (DTM) forms groups of session threads called partition groups. A partition group is a group of reader, writer, or transformation threads that run in a single DTM process. A partition group might include one or more pipeline stages. A pipeline stage is the section of a pipeline executed between any two partition points. Some transformations are not partitionable across a grid. When a transformation is not partitionable across a grid, the DTM creates a single partition group for the transformation threads and runs those threads on a single node.
