Expand Configuration and Management Manual (H06.21+, J06.10+)

Planning a Network Design
Expand Configuration and Management Manual — 529522-013
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Selecting Special Features
For more information on the multi-CPU paths, see Multi-CPU Feature on page 17-72.
Selecting Special Features
The Expand subsystem includes several special features that enable you to profoundly
affect the operation of your network. These features include the:
•
Multipacket frame feature
•
Variable packet size feature
•
Congestion control feature
This subsection provides information to help you determine when to use these
features.
Multipacket Frame Feature
The multipacket frame feature is a performance enhancement designed to increase
throughput and decrease processor overhead for all connection types.
The multipacket frame feature is especially suited for paths in which the default frame
size of 132 words (256-byte packets) is used. For this kind of path, a large increase in
throughput, along with less total processor consumption, should be obtained for a
given load. These advantages are achieved by reducing the use of the message
system and requiring less processing by the Expand line-handler process.
The multipacket frame feature can also improve the efficiency of direct-connect and
satellite-connect lines in which the average message size is less than 500 bytes. For
these types of connections, the multipacket frame feature decreases the number of
interrupts, reduces the number of times the Expand line-handler process is dispatched,
and causes a reduction in processor use.
Online transaction processing (OL
TP) benefits the most from the multipacket frame
feature.
For a complete technical overview of the multipacket frame feature, see Multipacket
Frame Feature on page 17-63.
Variable Packet Size Feature
The variable packet size feature is a performance enhancement designed to increase
bulk transfers over all connection types.
The variable packet size feature provides these benefits:
•
Reduces per-message processor cost for large message sizes
•
Reduces network bandwidth used for Expand overhead for large messages
•
Increases potential throughput in high-bandwidth Expand paths
Note. You use the SUPERPATH_ON modifier to configure an Expand line-handler process as
part of a multi-CPU path. If you configure parallel paths between two nodes without using the
SUPERPATH_ON modifier, only one path is used at a given time.