When the Data Integration Service runs jobs in separate local or remote processes, the Data Integration Service maintains a pool of reusable DTM processes.
The DTM process pool includes DTM processes that are running jobs and DTM processes that are idle. Each running DTM process in the pool is reserved for use by one of the following groups of related jobs:
Jobs from the same deployed application
Mapping jobs run from the Developer tool
For example, if you run two jobs from the same deployed application, two DTM instances are created in the same DTM process. If you run a preview job, the DTM instance is created in a different DTM process.
When a DTM process finishes running a job, the process closes the DTM instance. When the DTM process finishes running all jobs, the DTM process is released to the pool as an idle DTM process. An idle DTM process is available to run any type of job.