A run of records that contain the stored key is passed to the same output stream. When the key of the input record is not equal to the stored key, the next output stream is selected and the run of records is passed to this stream. The record from the secondary input stream specifies the number or identifier of the stream to receive the corresponding record from the primary input stream. This word is the stream identifier for the output stream that should receive the corresponding record from the primary input stream. Records are read from the primary input stream.
Records are, in general, written to all connected output streams.
The corresponding input records are not consumed. An input record will then be made available. It is unlikely to be efficient to distribute work amongst stages that do not in some way connect to a different task or another virtual machine.