The DTM allocates process memory for the session and divides it into buffers. This is also known as buffer memory. The DTM uses multiple threads to process data in a session. The main DTM thread is called the master thread.
The master thread creates and manages other threads. The master thread for a session can create mapping, pre-session, post-session, reader, transformation, and writer threads.
For each target load order group in a mapping, the master thread can create several threads. The types of threads depend on the session properties and the transformations in the mapping. The number of threads depends on the partitioning information for each target load order group in the mapping.
The following figure shows the threads the master thread creates for a simple mapping that contains one target load order group:
One reader thread.
One transformation thread.
One writer thread.
The mapping contains a single partition. In this case, the master thread creates one reader, one transformation, and one writer thread to process the data. The reader thread controls how the PowerCenter Integration Service process extracts source data and passes it to the source qualifier, the transformation thread controls how the PowerCenter Integration Service process handles the data, and the writer thread controls how the PowerCenter Integration Service process loads data to the target.
When the pipeline contains
a source definition, source qualifier, and a target definition, the data bypasses the transformation threads, proceeding directly from the reader buffers to the writer. This type of pipeline is a pass-through pipeline.
The following figure shows the threads for a pass-through pipeline with one partition: