When AMPs process a SELECT statement, they obtain the required rows. The BYNET transmits messages to and from the AMPS and PEs. An AMP step goes 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 Example: SQL Request. If access is through a primary index and a request is for a single row, the PE transmits steps to a single AMP (see PE1). If the request is for many rows (an all-AMP request), the PE makes the BYNET broadcast the steps to all AMPs (see PE2). To minimize system overhead, the PE can send a step to a subset of AMPs.