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Quick References for IBM Mainframe Programming

MAINFRAME COMPUTERS

What is Mainframe Computer?

 

IBMMAINFRAMES.com Definition:

 

                                   A Mainframe Computer is a high performance Multi User computer system which is the most scalable, available, reliable and secured machine in the world capable of performing some Million Instructions per second (upto 569,632 MIPS) with the following characteristics:

1) Reliable single-thread performance

2) Maximum I/O connectivity

3) Maximum I/O bandwidth

4) Reliability, Availability & Serviceability (RAS)

5) Unbreakable Security & Scalability (USS)

 

Mainframe Computer

 

                                                                   The IBM Mainframe Computer processed the data for the first lunar landing. An IBM Mainframe S/360 Model 75 was used for the communications across NASA and the moving spacecraft and processed the whole data for the first lunar landing and safe return from the moon which is 356,000 kms away. This computer was used by Neil Armstrong to calculate lift-off data required to launch the Lunar Module off the Moon's surface and enable it to rendezvous with Command Module pilot Michael Collins for the flight back to Earth. At that time, the 6MB program written by IBM for NASA�s systems was the most complex computer software ever written. Without the IBM Mainframe computer Neil Armstrong wouldn't have been able to bring a piece of the moon back to earth or have walked on the moon.

                                                                    Today, applications of mainframe computers various from computing the Random number series to census, industry and consumer statistics, ERP and financial transaction processing... 

 

Classification of Computer Systems

1) Micro Computer

2) WorkStation Computer

3) Mini Computer

4) Mainframe Computer

5) Super Computer

 

 

Classification of Computers

Micro Computer

A small, single-user computer based on a microprocessor. In addition to the microprocessor, a micro computer has a keyboard for entering data, a display monitor for displaying information, and a storage device like hard disk for saving data.

Example:  IBM Personal Computer


 

Workstation Computer

A powerful, single-user computer. A workstation is like a personal computer, but it has a more powerful microprocessor like Intel Xeon processors and a higher-quality monitor.

Example:  AVID Editing Suites

 

Mini Computer

A multi-user computer capable of supporting hundreds of users simultaneously, usually smaller than mainframes capable of supporting from 4 to about 100 users simultaneously.


Example:  IBM AS/400

 

Mainframe Computer

Mainframe computers, also knows as Big Iron or dinosaur, are powerful multi-user computer capable of supporting thousands of users simultaneously, used mainly by large organizations for critical applications, typically bulk data processing such as census, industry and consumer statistics, ERP, and financial transaction processing..

The distinction between small mainframes and minicomputers is vague, depending really on how the manufacturer wants to market its machines.

Example:  IBM s/390

 

Super Computer

The fastest type of computer. Supercomputers are very expensive and are employed for specialized applications that require immense amounts of mathematical calculations. For example, weather forecasting requires a supercomputer. Other uses of supercomputers include animated graphics, fluid dynamic calculations, nuclear energy research, and petroleum exploration.

The term "Super Computing" was first used by New York World newspaper in 1929 to refer to large custom-built tabulators IBM made for Columbia University.

Example:  IBM BlueGene

 

Super Computer vs Mainframe Computer

 

Supercomputers generally focus on problems which are limited by calculation speed while mainframes focus on problems which are limited by input/output and reliability ("throughput computing") and on solving multiple business problems concurrently (mixed workload).

 

In some ways, mainframes are more powerful than supercomputers because they support more simultaneous programs. But supercomputers can execute a single program faster than a mainframe. The distinction between small mainframes and minicomputers is vague, depending really on how the manufacturer wants to market its machines.

 

Supercomputers are often purpose-built for one or a very few specific institutional tasks (e.g. simulation and modeling). Mainframes typically handle a wider variety of tasks (e.g. data processing, warehousing). Consequently, most supercomputers can be one-off designs, whereas mainframes typically form part of a manufacturer's standard model lineup.



Mainframes tend to have numerous ancillary service processors assisting their main central processors (for cryptographic support, I/O handling, monitoring, memory handling, etc.) so that the actual "processor count" is much higher than would otherwise be obvious. Supercomputer design tends not to include as many service processors since they don't appreciably add to raw number-crunching power.
 

The ability of Mainframes are often measured in millions of instructions per second (MIPS), but supercomputers are measured in floating point operations per second (FLOPS). Commonly supercomputers are used for scientific problems, while mainframes are used for business processing.

 

Characteristics of Mainframe

 

1) Reliability  

 

Reliability is a measurement of the ability of a system to continue processing without failure. System Z servers have reported an 'Mean Time to Failure' of 40 years, that means they are guaranteed to run continuously for 40 years without any failure.

 

2) Scalability

 

Scalability is the capability of a system, network, or process to handle a growing amount of work, or its potential to be enlarged in order to accommodate that growth. Mainframes exhibit scalability characteristics in both hardware and software, with the ability to run multiple copies of the operating system software as a single entity called Sysplex.

 

3) Availability

 

The degree to which a system, subsystem or equipment is in a specified operable and committable state at the start of a mission, when the mission is called for at an unknown, i.e. a random, time. The  Z series Mainframe Systems are designed to provide an availability of 99.999%.

 

4) Compatibility

 

A family of computer models is said to be compatible if certain software that runs on one of the models can also be run on all other models of the family. Programs that were written for the IBM OS/360 and later models, will still run quite happily on the latest version of IBM Z/OS, usually without even a recompile or re-assembly (that's nearly 50 years of continuous upward compatibility and reliability).

 

5) Serviceability

 

Serviceability is an expression of the ease with which a component, device or system can be maintained and repaired. The logging facility of Mainframe system can easily tell why a failure occurred. This capability allows for the replacement of hardware and software elements while impacting as little of the operational system as possible.

 

Peripherals used in Mainframe

 

1) 3270 Terminal

 

IBM 3270 Terminals are dumb computers with a monitor and keyboard used to communicate with a Mainframe, often from a remote location. In reality, mainframe interfaces today look much the same as those for personal computers. Now a days, people around the world connect to the Mainframe Computer, remotely over internet, from their work-place or home using a normal PC running a software that pretends to be a dumb-terminal. You don�t have to sit physically near a Mainframe CPU to do your work. Picture of IBM 3270 terminals from 1981.

 

IBM 3270 Terminal Computer

 

2) Hard Drive (DASD)

 

In Mainframe, DASD (Direct Access Storage Device) volumes are used for storing data and executable programs (including the operating system itself), and for temporary working storage. IBM 3390 model DASD disk drives are commonly used on mainframes. The 3390 Model 9 was the last Single Large Expensive Disk drive announced by IBM. Since the manufacture of actual 3390s ended, Modern DASD used in mainframes only very rarely consist of single disk-drives. Now a days DASD storage has been emulated on FBA (PC / Unix disk), usually in a RAID 5 configuration. The current equivalent device for a 3390 unit is an IBM 2105 Enterprise Storage Server. Applications and system software written for 3390 drives run perfectly on IBM 2105 drives with no revisions. The picture below shows a single 3390 DASD disk drive (3390 unit typically has eight or more disk drives).

IBM 3390 Disk Drive

 

3) Tape Drive

 

The IBM 3480 tape subsystem marked a major milestone in tape storage with its square cartridges. It replaced the traditional round tape reels we often see spinning away in old sci-fi films. The first 3480 tape drives were introduced in 1984. In 1986, IBM added a hardware-based data compression option: Improved Data Recording Capability (IDRC). A 3480 tape drive with IDRC could record up to 400 megabytes instead of 200MB on a single tape. A 3480 tape drive with IDRC uses the same data cartridges as a standard 3480 tape drive. It can read and write standard 3480 tapes. In 2011 IBM introduced the fourth generation of the IBM 3592 Enterprise Tape Drive, the IBM TS1140. The TS1140 can hold twenty thousands times more data than the 3480. Picture of IBM 3480 Magnetic Tape Subsystem.

 

IBM Tape Drive 3480

 

4) Printers

 

The IBM 1403 line printer was introduced as part of the IBM 1401 computer in 1959. The IBM 3800 laser printer of 1975 had a speed of 180 pages per minute in preparing bank statements, premium notices and other high-volume documents. IBM partnered with Hitachi to OEM an Hitachi developed printer, released as the IBM 3900 in late 1991. The IBM 6400 family of line matrix printers are modern high speed business computer printers introduced by IBM in 1995. The new Infoprint 6500 printers attach to a wide spectrum of IBM systems from IBM mainframes and parallel servers to PCs. An IBM Infopint printer in picture:

 

IBM Printer Infoprint

 

Characteristics of Mainframe Operating System

 

1) Multiple Virtual Storage

 

Virtual storage is a technique that lets a large amount of main storage be simulated by a processor that actually has a smaller amount of real storage. For example, a processor that has 256 MB of real storage might use virtual storage to simulate 512 MB of main storage. To do this, the computer uses disk storage as an extension of real storage. In Personal Computer we use Single Virtual Storage in which several tasks share the same address space. Mainframe computer uses Multiple Virtual Storage (MVS) which has the facility to store several tasks in different address space and hence the name.
 

 

2) Multiprogramming & Multithreading

 

Multiprogramming is a technique used to utilize maximum CPU time by running multiple programs simultaneously. More than one task/program/job can reside into the main memory at one point of time. This ability of the OS is called multiprogramming. To run multiple jobs asynchronously, Mainframe uses Initiators. Preventing two users from accessing the same data at the same time is critical to operating system and the ability to do this is one of the defining characteristics of the Mainframe OS. Multithreading is the ability of an operating system to execute different parts of a program, called threads, simultaneously.

 

3) Spooling

 

Spooling refers to a process of communicating data to another program by placing it in a temporary working area. Spooling is a method for queuing and holding data for input or output. The Mainframe operating system uses one or more disk data sets for spooling. Input jobs and printed output from many jobs are stored in the single (conceptual) spool data set.

 

4) Batch Processing

 

Batch processing is execution of a series of programs on a computer without human interaction.

 

5) Time-sharing

 

In a time sharing system, each user has access to the system through a terminal device. Instead of submitting jobs that are scheduled for later execution as in batch processing, the user enters commands that are processed immediately. As a result, time sharing is sometimes called online processing because it lets users interact directly with the computer.

 

LIST OF IBM MAINFRAMES:

IBM s/360

s/370

ES/9000

S/390

Z/900

Z/800

Z/990

Z/890

Z9 EC & BC

Z10

Z13

 

LIST OF MAINFRAME OPERATING SYSTEM:

DOS/360

OS/360

OS/VS1

OS/VS2

MVS/SP

MVS/XA

MUSIC/SP

MVS/ESA

VSA/ESA

VM/ESA

TPF

OS/390

OpenSolaris for System Z

LINUX ON System Z

UTS (MAINFRAME UNIX)

Z/TPF

Z/VM

Z/VSE

Z/OS

 

LIST OF MAINFRAME SUB SYSTEMS:

TSO, TSO/E

RACF

SMS

DFSMS/MVS, DFSMS/VM

ACF2, ASF-DCF,CA, ACF/VTAM

DFSMS, DFSORT

SMP, SMP/E

IEF, DFA

JES/1, JES/2, JES/3

 

SOFTWARE RUNNING UNDER MAINFRAME OS:

VS COBOL II, IBM COBOL, ENTERPRISE COBOL

C/370, C++/MVS, JAVA

CICS/VM, CICS/MVS, CICS/ESA, CICS/TS

DB2/UDB

CLIST, REXX/370

NATURAL, ADABAS

ASSEMBLER, IBM SAA AD/CYCLE

IMS DB/DC

WEBSPHERE, MQSeries

FILEAID, XPEDITOR, COOL-GEN

ISPF, ISPF/PDF, DATA-XPERT, CHANGEMAN

IDEAL, ENDEVOR, EASYTRIEVE

IDMS, ADS/O, VISION PLUS, FOCUS/ DB

CARDPAC, SMP/E, TIVOLI

DFSORT, SYNCSOFT, PANAVALET

TRACEMASTER, INTERTEST, ABEND-AID

ESP, MS MAIL, ZzIP

 

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