Databases Reference
In-Depth Information
Table 6.4
Summary of Three Major Interconnect Technologies
the database has to send and manage only one message and one response, lowering the
cost and increasing the performance.
When it is time to return results to a user or application, the BYNET supplies the merge
function. Unlike other parallel databases that pull the result set together in one node to
deliver the appropriately sorted result, Teradata leaves each portion of the result set on
the node where it was created, sorted locally. The merge function collates just enough of
the result to fill the user's buffer with result records, then waits for the user to request
more rows. Merge makes returning results a scalable operation regardless of their size.
Finally the third and most effective way to avoid communication costs between
nodes is to avoid internode communication completely by using logical nodes rather
than physical data nodes. Logical nodes will be described in more detail below in Sec-
tion 6.8. Using logical nodes, a single larger multiprocessor system is used to house sev-
eral data nodes. Since multiple data nodes reside on the same physical server, the intern-
ode communication between them does not require the use of an external network (or
switch) and data can be transferred between them using shared memory.
