AS400 Architecture Basics

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iSeries

Lecture 2


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iSeries architecture

Several architectural features of the iSeries Architecture

distinguish the system from other machines in industry,including UNIX and Windows NT. These features [thefive sacred architectural principles] include:

Technology Independence [ due to the two-part operating

system and TIMI]

Object-based design

Hardware integration

Software integration

Single level store


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iSeries architecture

Several architectural features of the iSeries Architecture distinguish the system fromother machines in industry, including UNIX and Windows NT. These features [the five

sacred architectural principles] include:

Two-part operating system

Technology-independent machine interface (TIMI)

Object-based system

Single-level storage

Separate I/O processors

Multiple data busses

High degree of integration

Open Standards

Logical partitions and many operating systems


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iSeries 800 to 890
http://www-132.ibm.com/content/home/store_IBMPublicUSA/en_US/eServer/iSeries/hardware/medlarge/890/index.htmlhttp://www-132.ibm.com/content/home/store_IBMPublicUSA/en_US/eServer/iSeries/hardware/smallmed/800/index.html


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Two-part operating system

There are two components to the operating system software on aniSeries server.unique in the industry. The two components are System Licensed Internal Code(SLIC) and

Operating System/400(OS/400).

SLIC provides the TIMI with

process control resource management

integrated SQL database

Security

Communications

file system

temp storage JVM, and other primitives.

SLIC is a layer of software at the lowest level, much like a Unix kernel,only far more functional.


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Two-part operating system (cont.)

Operating System/400(OS/400).

Provides the functions that present and work with these

services to the user and to applications.

OS/400 also provides a vast range of high-level

language (such as C/C++, COBOL, RPG, FORTRAN)

runtime functions.

OS/400 interacts with the client-server graphical user

interface [iSeries Navigator].


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Technology-Independent Machine Interface

SLIC, is the Optimizing Translatorconverts applications

to the proper instruction set for the processor. After

translation, which is much like the last part of a compile

process, the resultant code is maintained with the program

object, for reuse.


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In iSerieschanges to processor hardware and firmware do notaffect the operating system

middleware or

business applications.

The heart of this ability to change without disrupting customers andtheir applications is the Technology-Independent Machine Interface (TIMI).

Applications do not have to rewritten or even recompiled to exploit

new hardware technologies.

This permits only iSeries servers to make technology advances inthe hardware, such as storage, memory, and processor technology,while protecting end-users' investments in existing applications


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All iSeries models

smallesta few hundred users Largesthundreds of thousands of users

share the same software architecture, including the TIMI.

This permits applications to scale across the entire product line,

from the smallest to the largest models.

48-bit [CISC]64-bit [RISC]

Digital Equipment case !! 3264 128-bit ?


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Object-based system

OS/400 keeps all information as objects.

All program and operating system information, such as: user profiles, database files, programs, printer queue etc. has its

associated object type stored with the information.

In the iSeries architecture, the object type determines

how the object can be used (which methods). For example, it is impossible to corrupt a program object by

modifying its code sequence data, as if it were a file. Becausethe system knows the object is a program, it will only allow validprogram operations (run, backup). Thus, with no write method,

iSeries program objects are immune to a true virus.

Simple stream data files, such as MP3 audio files, are stored asstream-file objects with familiar open, read, and write operations.


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Object-based system


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Single-Level Storage

The iSeries architecture specifies a single very, very large virtualaddress space known as Single-Level Storage (SLS).

All objects, programs, files, users, data, working space, databasetables... everything, resides in this storage space.

This storage space is addressed using 128-bit pointers. It is divided

into sections, including Temporary and Persistent. This distinctionrefers to betweenre-boots. For examples, a user profile is inPersistent, and a shared memory segment is in Temporary.


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Single-Level Storage


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Separate I/O processors and multiple data busses

The hardware side of the iSeries architecture emphasizes the use ofspecialized, intelligent I/O).

Tasks such as disk, network, tape, and terminal I/O are offloaded toa variety of dedicated processors, allowing the main processor(s) towork on application execution.

Most of these I/O processors are PowerPC-based high-speed RISC

processors running a small, self-contained operating system.


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High Degree of Integration

Another defining characteristic of the iSeries architecture is the highdegree of integration both above and below the TIMI.

For example, DB2 for OS/400 is a native relational database managementsystem. That is, DB2/400 is shipped with every system and highlyintegrated into the licensed internal code and the operating system.

The following are areas of iSeries's integration:

Relational database management system (DB/2 for OS/400) Transaction monitor

Communications

Security

Internet serving

User and group administration

Printer management

Job (process) management Backup and recovery

Online help

Electronic customer support

System and network management


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Open standards

The iSeries heritage is based on integrationemphasis has been on providing anintegrated solution.

Although OS/400 is proprietary, IBM has insured an iSeries focus on "open" systemapplications. OS/400 provides numerous industry standards which facilitateapplication portability from other platforms and interoperability with other hardwareplatforms.

IBM's strategy for implementing POSIX, Single UNIX Specification and XPG4 functionshas been to provide APIs and system interfaces that are most valuable to most

vendors developing commercial business applications. OS/400 portability supportincludes:

Asynchronous signals

BSD sockets

Environment variables

Interprocess communication (IPC)

File Systems

POSIX file system Process control

TCP/IP

TI-RPC

Multi-threading (both POSIX and Java)


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iSeries is theuniversal server.

OS/400

Linux

Unix,

Windows

applications all run on iSeries servers.

A single server may optionallybe divided into several partitions, eachof which receives a dedicated set of resources, including processorand memory.

The primary partition must be OS/400, but the other partitions can run,as of this writing, different versions of OS/400 and Linux.


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Logical partitions and many operating systems (cont.)

Linux distributions, provided by several vendors, run in logicalpartition(s) of an iSeries server.

Windows applications run on an iSeries server on an optional plug-in Intel processor.

Rather than run an instance of a Unix operating system, applicationsfrom AIX run inside an OS/400 job, completely and seamlessly

integrated into OS/400. This option is the OS/400 Portable Application Solution Environment

(OS/400 PASE). PASE provides a very easy way to drop in, oftenunmodified, a Unix application on iSeries.


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Open standards

The iSeries heritage is based on integrationemphasis has been on providing anintegrated solution.

Although OS/400 is proprietary, IBM has insured an iSeries focus on "open" systemapplications. OS/400 provides numerous industry standards which facilitateapplication portability from other platforms and interoperability with other hardwareplatforms.

IBM's strategy for implementing POSIX, Single UNIX Specification and XPG4 functionshas been to provide APIs and system interfaces that are most valuable to most

vendors developing commercial business applications. OS/400 portability supportincludes:

Asynchronous signals

BSD sockets

Environment variables

Interprocess communication (IPC)

File Systems

POSIX file system Process control

TCP/IP

TI-RPC

Multi-threading (both POSIX and Java)

Documents

AS400 Architecture Basics