When you run a PowerCenter Integration Service on a grid, a master service process runs on one node and worker service processes run on the remaining nodes in the grid. The master service process runs the workflow and workflow tasks, and it distributes the Session, Command, and predefined Event-Wait tasks to itself and other nodes. A DTM process runs on each node where a session runs. If you run a session on a grid, a worker service process can run multiple DTM processes on different nodes to distribute session threads.