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

Subsystem Description
Expand Configuration and Management Manual — 529522-013
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Shared Memory Area for QIO
The SCF attribute EXTMEMSIZE n allows you to specify the base size of extended
memory for the pool, from a default of 2 megabytes to as much as 32 megabytes.
This extra memory will be of invaluable help to applications such as the Remote
Database Facility (RDF) which in the past suffered from memory pool problems and
thus reduced performance.
Shared Memory Area for QIO
QIO is a mechanism for transferring data between processes through a shared
memory segment. QIO is used by Expand-over-IP and Expand-over-ATM line-handler
processes. The Expand-over-IP line-handler process uses QIO to transfer data to its
associated NonStop TCP/IP process. The Expand-over-ATM line-handler process uses
QIO to transfer data to its associated ATM line.
The QIO subsystem has been enhanced as of G06.17 to allow you to have more
control over certain aspects of memory management. You can now configure QIO to
run in the Kseg2 memory segment and you can also control where QIO runs in the flat
memory segment. Configuring QIO to run in Kseg2 can improve performance for
NonStop TCP/IPv6 but also imposes constraints that affect all QIO clients (including
NonStop TCP/IPv6). As discussed in the QIO Configuration and Management Manual,
you must consider these constraints in addition to a variety of other factors before
changing the default QIO configuration.
Some of the constraints affecting NonStop TCP/IPv6 (in addition to other QIO clients)
include the reduction of QIO memory space to 128 MB when QIO is moved to Kseg2.
This restriction impacts the number of LIFs that you can configure on your system
because LIFs use QIO memory. This restriction also impacts the number of sockets
that can be opened because open sockets use QIO memory as well. Therefore, 128
MB cannot be sufficient for your NonStop TCP/IPv6 or other QIO client needs.
For more information on the QIO subsystem, see the QIO Configuration and
Management Manual.
Note. QIO memory is not the same as Extended Memory. Expand-over-ATM and Expand-
over-IP have both QIO and Extended Memory requirements.
Note. The default configuration for the QIO subsystem has not changed.
Whether you use the default QIO configuration or o
ne of the newly-supported custom
configurations, you do not need to change anything in NonStop TCP/IPv6; all changes are
made in the QIO subsystem.