AMPs obtain the rows required to process the requests (assuming that the AMPs are processing a SELECT statement). The BYNET transmits messages to and from the AMPS and PEs. An AMP step can be sent to one of the following:
- One AMP
- A selected set of AMPs, called a dynamic BYNET group
- All AMPs in the system
The following figure is based on the example in the next section. If access is through a primary index and a request is for a single row, the PE transmits steps to a single AMP, as shown at PE1. If the request is for many rows (an all-AMP request), the PE makes the BYNET broadcast the steps to all AMPs, as shown in PE2. To minimize system overhead, the PE can send a step to a subset of AMPs, when appropriate.
