IBM Communications Server for AIX, V6 New Features and Implementation Scenarios

214 IBM Communications Server for AIX, V6: New Features and Implementation Scenarios

The latest level for all these filesets may be downloaded from the following

URL:

http://service.software.ibm.com/cgi-bin/support/rs6000.support/downloads

It is possible to have a CS/AIX configuration that does not require any fileset

to be installed:

• Applications that use HPR/IP (Enterprise Extender)

• Applications that use APPC over IP

• U-shaped sessions (stays in the RS/6000 box)

• An application that uses one of the APIs that do not leave the box such as

a NOF or CSV application

13.2 64-bit architecture and benefits

From an operation point of view, an architecture is said to be 64-bit when:

• It can handle 64-bit-long data. In other words, a contiguous block of 64 bits

(8 bytes) in memory is defined as one of the elementary units that the

CPU can handle. This means that the instruction set includes instructions

for moving 64-bit-long data and instructions for performing arithmetic

operations on 64-bit-long integers.

• It generates 64-bit-long addresses, both as effective addresses (the

addresses generated and used by machine instructions) and as physical

addresses (those that address the memory cards plugged into the

machine memory slots). Individual processor implementations may

generate shorter physical addresses, but the architecture must support

64-bit addresses.

The distinguishing technical features and benefits of 64-bit computing as

contrasted to 32-bit computing are:

• 64-bit integer computation, using hardware with 64-bit general purpose

registers

• Large file support

• Large application virtual address spaces

• Large physical memory support

13.2.1 64-bit integer computation

Native 64-bit integer computation is provided by 64-bit hardware, and utilized

by programs computing on 64-bit data types. While there are some

Chapter 13. 64-bit SNA applications 215

specialized applications that need to do computation on integer numbers

larger than 2

32

, the key benefit of this capability is in performing arithmetic

operations on pointers in 64-bit programs. Floating point computation already

includes 64-bit precision on all RS/6000 systems.

13.2.2 Large file support

The ability to create and maintain very large file systems is increasingly

important for many users. In particular, data warehousing applications, and

scientific and multimedia applications frequently require this support.

The ability to address data in files larger that 2 GB (32-bit addresses)

requires that a program be able to specify file offsets larger than a 32-bit

number. This capability is generally considered to be a 64-bit computing

function even though it does not require 64-bit hardware support. AIX Version

4.2 provided this capability for 32-bit programs, and AIX Version 4.3 provides

it for 64-bit programs as well. Since it does not depend on 64-bit hardware,

this function can be used on any RS/6000 system running the appropriate

release of AIX.

There is, however, synergy between large file support and 64-bit hardware

capabilities, in that a 64-bit program can have much larger portions of 64-bit

files in its address space, as well as in system memory, at one time, than a

32-bit system could provide.

13.2.3 Large application virtual address spaces

In 32-bit systems, an individual program, or process, may typically have

between 2 GB and 4 GB of virtual address space for its own use to contain

instructions and data. With 64-bit computing, applications may run in a 64-bit

address space, where an individual program’s addressability becomes

measured in terabytes (TB). Types of applications that currently understand

how to exploit this opportunity include the following:

• Some database management programs use a large address space for

scalability, in order to maintain very large data buffers in memory, reducing

the amount of I/O they need to perform. Using a large address space, they

can supply data to client applications at the pace needed to sustain the

high transaction rate potential afforded by many of the new processors in

the industry.

• In certain cases, database management programs or customer

applications may benefit from keeping an entire database or large file

immediately accessible in memory. Read-only data lends itself most