After the load manager performs validations for the session, it creates the DTM process. The DTM process is the second process associated with the session run. The primary purpose of the DTM process is to create and manage threads that carry out the session tasks.

· The DTM allocates process memory for the session and divide it into buffers. This is also known as buffer memory. It creates the main thread, which is called the master thread. The master thread creates and manages all other threads.

· If we partition a session, the DTM creates a set of threads for each partition to allow concurrent processing.. When Informatica server writes messages to the session log it includes thread type and thread ID.

Following are the types of threads that DTM creates:

Master Thread - Main thread of the DTM process. Creates and manages all other threads.

Mapping Thread - One Thread to Each Session. Fetches Session and Mapping Information.

Pre and Post Session Thread - One Thread each to Perform Pre and Post Session Operations.

Reader Thread - One Thread for Each Partition for Each Source Pipeline.

Writer Thread - One Thread for Each Partition if target exist in the source pipeline write to the target.

Transformation Thread - One or More Transformation Thread For Each Partition.

When the workflow reaches a session, the Integration Service process starts
the DTM process. The DTM is the process associated with the session and it
performs the following tasks:

1. Retrieves and validates session information from the repository.

2. Performs pushdown optimization when the session is configured for
pushdown optimization.

3. Adds partitions to the session when the session is configured for dynamic
partitioning.

4. Forms partition groups when the session is configured to run on a grid.

5. Expands the service process variables, session, and mapping variables and
parameters.

6. Creates the session log.

7. Validates source and target code pages.

8. Verifies connection object permissions.

9. Runs pre-session shell commands, stored procedures and SQL.

10. Sends a request to start worker DTM processes on other nodes when the
session is configured to run on a grid.

11. Creates and runs mapping, reader, writer, and transformation threads to
extract, transform, and load data.

12. Runs post-session stored procedures, SQL, and shell commands

13. Sends post-session email.