Reads the session information
The PowerCenter Integration Service process provides the DTM with session instance information when it starts the DTM. The DTM retrieves the mapping and session metadata from the repository and validates it.
Performs pushdown optimization
If the session is configured for pushdown optimization, the DTM runs an SQL statement to push transformation logic to the source or target database.
Creates dynamic partitions
The DTM adds partitions to the session if you configure the session for dynamic partitioning. The DTM scales the number of session partitions based on factors such as source database partitions or the number of nodes in a grid.
Forms partition groups
If you run a session on a grid, the DTM forms partition groups. A partition group is a group of reader, writer, and transformation threads that runs in a single DTM process. The DTM process forms partition groups and distributes them to worker DTM processes running on nodes in the grid.
Expands variables and parameters
If the workflow uses a parameter file, the PowerCenter Integration Service process sends the parameter file to the DTM when it starts the DTM. The DTM creates and expands session-level, service-level, and mapping-level variables and parameters.
Creates the session log
The DTM creates logs for the session. The session log contains a complete history of the session run, including initialization, transformation, status, and error messages. You can use information in the session log in conjunction with the PowerCenter Integration Service log and the workflow log to troubleshoot system or session problems.
Validates code pages
The PowerCenter Integration Service processes data internally using the UCS-2 character set. When you disable data code page validation, the PowerCenter Integration Service verifies that the source query, target query, lookup database query, and stored procedure call text convert from the source, target, lookup, or stored procedure data code page to the UCS-2 character set without loss of data in conversion. If the PowerCenter Integration Service encounters an error when converting data, it writes an error message to the session log.
Verifies connection object permissions
After validating the session code pages, the DTM verifies permissions for connection objects used in the session. The DTM verifies that the user who started or scheduled the workflow has execute permissions for connection objects associated with the session.
Starts worker DTM processes
The DTM sends a request to the PowerCenter Integration Service process to start worker DTM processes on other nodes when the session is configured to run on a grid.
Runs pre-session operations
After verifying connection object permissions, the DTM runs pre-session shell commands. The DTM then runs pre-session stored procedures and SQL commands.
Runs the processing threads
After initializing the session, the DTM uses reader, transformation, and writer threads to extract, transform, and load data. The number of threads the DTM uses to run the session depends on the number of partitions configured for the session.
Runs post-session operations
After the DTM runs the processing threads, it runs post-session SQL commands and stored procedures. The DTM then runs post-session shell commands.
Sends post-session email
When the session finishes, the DTM composes and sends email that reports session completion or failure. If the DTM terminates abnormally, the PowerCenter Integration Service process sends post-session email.