When you run a session on a grid, the master service process runs the workflow and all tasks except Session, Command, and predefined Event-Wait tasks as it does when you run a workflow on a grid. The Scheduler runs on the master service process node, so it uses the date and time for the master service process node to start scheduled workflows. In addition, the Load Balancer distributes session threads to DTM processes running on different nodes.
When you run a session on a grid, the Load Balancer distributes session threads based on the following factors:
. The Load Balancer verifies which nodes are currently running, enabled, and available for task dispatch.
. If the Integration Service is configured to check resources, it identifies nodes that have resources required by mapping objects in the session.
The Load Balancer dispatches groups of session threads to separate nodes based on the partitioning configuration.
You might want to configure a session to run on a grid when the workflow contains a session that takes a long time to run.
For example, a workflow contains a session with one partition. To balance the load, you configure the session to run on a grid and configure the Integration Service to check resources. The Load Balancer distributes the reader, writer, and transformation threads to DTM processes running on the nodes in the grid. The reader threads require a resource, so the Load Balancer distributes them to a DTM process on the node where resources are available.
The following image shows session threads distributed to DTM processes running on nodes in a grid:
Reader threads run on node where resources are available.