Download Note 2

iSeries
Lecture 2
iSeries architecture
Several architectural features of the iSeries Architecture
distinguish the system from other machines in industry,
including UNIX and Windows NT. These features [“the
five 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
iSeries architecture
Several architectural features of the iSeries Architecture distinguish the system from
other 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
iSeries 800 to 890
Two-part operating system
• There are two components to the operating system software on an
iSeries 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
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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.
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].
Technology-Independent Machine Interface
SLIC, is the Optimizing Translator converts 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.
Two-part operating system (cont.)
• In iSeries  changes to processor hardware and firmware do not
affect the
– operating system
– middleware or
– business applications.
• The heart of this ability to change without disrupting customers and
their 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 in
the hardware, such as storage, memory, and processor technology,
while protecting end-users' investments in existing applications
Two-part operating system (cont.)
• All iSeries models
• smallest  a few hundred users
• Largest  hundreds 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 !! 32 – 64
• 128-bit ?
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. Because
the system knows the object is a program, it will only allow valid
program 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 as
stream-file objects with familiar open, read, and write operations.
Object-based system
Single-Level Storage
• The iSeries architecture specifies a single very, very large virtual
address space known as Single-Level Storage (SLS).
• All objects, programs, files, users, data, working space, database
tables... 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 distinction
refers to between re-boots. For examples, a user profile is in
Persistent, and a shared memory segment is in Temporary.
Single-Level Storage
Separate I/O processors and multiple data busses
• The hardware side of the iSeries architecture emphasizes the use of
specialized, intelligent I/O).
• Tasks such as disk, network, tape, and terminal I/O are offloaded to
a variety of dedicated processors, allowing the main processor(s) to
work on application execution.
• Most of these I/O processors are PowerPC-based high-speed RISC
processors running a small, self-contained operating system.
High Degree of Integration
• Another defining characteristic of the iSeries architecture is the high
degree of integration both above and below the TIMI.
– For example, DB2 for OS/400 is a native relational database management
system. That is, DB2/400 is shipped with every system and highly
integrated into the licensed internal code and the operating system.
• The following are areas of iSeries's integration:
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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
Open standards
The iSeries heritage is based on integration  emphasis has been on providing an
integrated solution.
Although OS/400 is proprietary, IBM has insured an iSeries focus on "open" system
applications. OS/400 provides numerous industry standards which facilitate
application portability from other platforms and interoperability with other hardware
platforms.
IBM's strategy for implementing POSIX, Single UNIX Specification and XPG4 functions
has been to provide APIs and system interfaces that are most valuable to most
vendors developing commercial business applications. OS/400 portability support
includes:
• 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)
Logical partitions and many operating systems
Logical partitions and many operating systems
iSeries is the universal server.
• OS/400
• Linux
• Unix,
• Windows
applications all run on iSeries servers.
A single server may optionally be divided into several partitions, each
of which receives a dedicated set of resources, including processor
and 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.
Logical partitions and many operating systems (cont.)
• Linux distributions, provided by several vendors, run in logical
partition(s) of an iSeries server.
• Windows applications run on an iSeries server on an optional plugin Intel processor.
• Rather than run an instance of a Unix operating system, applications
from 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, often
unmodified, a Unix application on iSeries.
Questions
• Compute-intensive [complex operations on small amount of data]
• Information-intensive [simple operations on a large amount of data]
•
Open standards
The iSeries heritage is based on integration  emphasis has been on providing an
integrated solution.
Although OS/400 is proprietary, IBM has insured an iSeries focus on "open" system
applications. OS/400 provides numerous industry standards which facilitate
application portability from other platforms and interoperability with other hardware
platforms.
IBM's strategy for implementing POSIX, Single UNIX Specification and XPG4 functions
has been to provide APIs and system interfaces that are most valuable to most
vendors developing commercial business applications. OS/400 portability support
includes:
• 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)