The 'Chunker' is the batch process executable which identifies the records to be processed. This process constructs 'chunks' of these records and writes them to the database, in effect assembling them in a queuing table called BatchProcessChunk. This table is populated at the beginning of batch processing, and each set of records to be processed is identified on this table by a chunk ID. Note that this assembly is transactional, and must succeed before any Streams can start their processing.
In addition to creating the chunks, the Chunker waits for all chunks to be processed by the Stream(s) and produces a summary report when they are all complete. In most cases only one instance of the Chunker is required for each batch process. Note that if the chunker fails after chunk assembly, it is possible to just restart it even if streaming has already commenced.