Basic MF Introduction

8/19/2019 Basic MF Introduction

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Classifcation o Computers

Computer systems used for business purposes can be divided in to three classes:Microcomputers, Minicomputers and Mainframe computers. Though these divisions areloosely based on the size of the computer systems, there are no hard and fast rules for

deciding exactly where one category ends and the next begin. Hence the largestminicomputer systems are often larger than the smallest mainframe computers.

The size! of a computer system is dependent on the size of a computer"s hardwareconfiguration, the nature of its applications, and the complexity of its system software.This helps us to classify a system as a microcomputer, minicomputer or mainframe.

#rrespective of size, all computers consist of two basic types of components. Those are processors and input$output %#$&' devices.

The processor consists of three parts: the Central (rocessing )nit, or C(), main storage

and device controllers. The C() executes instructions, main storage stores instructionsand data processed by the C() and device controllers let the C() and main storageconnect to #$& devices.

*ote: Though all computer systems consist of three basic components, the way thosecomponents are combined for a particular computer system varies depending on thesystem"s re+uirements.

Microcomputer or Personal Computer

Microcomputer is primarily intended for standalone use by an individual.Microcomputers are small, singleuser systems which provide a simple processor and -usta few input$output devices. This system consists of a processor with or / 01 of mainstorage, a 2eyboard, a display monitor, a printer, and a dis2ette drive with a capacity of /01 and a 344 01 of hard dis2. 5ifferent models are available, such as 5es2top, *oteboo2, 6aptop, Handheld, (almtop and (57.

Minicomputer

)nli2e microcomputers, most of the minicomputers provide more than one terminal so

that several users can use the system at a time. 8uch systems are referred to as multiuser systems!.

The Mini computer 9 Mini computers li2e the mainframe computers are used by businessorganization. The difference being that it can support the simultaneous wor2ing of up to44 users and is usually maintained in business organizations for the maintenance of

accounts and finances.


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What is Server Technology

7 server! is simply a computer, any computer that provides services! to other computers. #f you computer can share its files, it"s a file server. #f you turn iTunes music

sharing on, your computer becomes a music server. #f you have a shared printer, your computer has become a print server.

7 server is a computer program running to serve the re+uests of other programs, the=clients=. Thus, the =server= performs some computational tas2 on behalf of =clients=. Theclients either run on the same computer or connect through the networ2. 5epending onthe computing service that it offers it could be a database server, file server, mail server, print server, web server, or other.

;or example, when you enter a +uery in 0oogle, the +uery is sent from your computer over the internet to the 0oogle servers that store all the relevant web pages. The results

are sent bac2 by the server to your computer.

Be can find the following types of servers around the world:

• Database server (rovides database services to other computer programs or

computers

• Web server 8erver that HTT( clients connect to in order to send commands and

receive responses along with data contents

• Standalone server - mulator for client9server %webbased' programs

• Proxy server - 7cts as an intermediary for re+uests from clients see2ing

resources from other servers

7nd so onD

Do we need a server? Why?

5o we need a serverE! is a common +uestion. The real hidden +uestion is Bhat does aserver do for my organization, and do we need something that does that E!

8ervers can actually do a lot of different things, which is why it"s sometimes difficult todecide. However, for the 8mall to Mediumsized organization, a server typically serves!in any or all of the following roles:

• Central file storage

• 1ac2ups• mail

• *etwor2 printer sharing

• ;irewall

•


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8o D #n this globalization era, most of the business runs with datum from differentstates, countries and continents. )ndoubtedly, computers handsha2e across regions andthereby 8ervers become a standard icon for a 1usiness or &rganization.

8ervers often run for long periods without interruption and availability must often be veryhigh, ma2ing hardware reliability and durability extremely important. Those are ideallyvery fault tolerant and use specialized hardware with low failure rates in order tomaximize uptime, for even a shortterm failure can cost more than purchasing andinstalling the system.

Mainrame !s !t a Server?

Mainframes are 8ervers, the way we have clientserver computing today, but they are notcalled servers because the =clients= of a mainframe system are usually terminals. Theseare dumb terminals, which mean all the applications they run on big system. *othing is

being served to the client...all the wor2 is done on the big machine. 7 Mainframe isusually dedicated for one purpose li2e a 1an2 or Corporate.

0enerally Mainframe machines acts as a servers %but they are not called as servers'. @outhrow tas2s to the Mainframe machine, and the mainframe performs the processing, andstores the result. Many users throw re+uests to the Mainframe machine concurrently.Thus, as a mainframe operator, generally you would not be present physically near themachine, you operate it remotely. you have a 2eyboard and monitor connected to your Mainframe server. There would be thousands of terminals connected to a mainframeserver and many users can perform their tas2s on the mainframe server concurrently. @oumight sit in the wor2office of your company on a terminal and perform dataprocessing

on the Mainframes server located somewhere else.

8o different types of computers or technology acts as a 8erver%1ut not a server'. 8o a(ersonal computer can be a server, Mini computer can be a server, Mainframe computer can be a server and so on. 1ut these differ on some factor and especially on


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Reliability 7bility of a computerrelated hardware or software component toconsistently perform according to its specifications. #n a simple form, it is not only freefrom technical errors but also avoid such errors once it arrives!.7 reliable system

• Helps itself to avoid and detect faults.

• 5oes not silently continue and deliver results with corrupted data instead itcorrects or else stops and reports the corruption.

Availability The ratio of time a system or component is functional to the total time it isre+uired or expected to function. #t may be reported as minutes or hours of downtime per year. This can be expressed as a direct proportion %for example, >$4 or 4.>' or as a percentage %for example, >4F'.7 system with high availability

• This allows the system to stay operational even when faults do occur.

• 5isables the malfunctioning portion and continue operating at a reduced capacity.

Serviceability - Garious methods of easily diagnosing the system when problems arise.8ome systems have the ability to correct problems automatically before serious troubleoccurs.7 system supports serviceability

• 5etects potential problems in the initial stage to avoid system downtime.

• Hot swapping of components replacing computer system components without

shutting down the system.

Why is "%S important?


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Mainrame ( % #rie !ntro)

So$ what is Mainrame?

7 large, highlyfunctional business computer, descended from #1MAs 8ystem$I4, whichis capable of running thousands %or more' of concurrent applications, serving millions %or more' of concurrent users at greater than >>F busy with >>.>>>F or bettter uptime andno degradation in service. #t continues to be the computer that handles much of theworldAs most critical business data processing, with so much reliability, availability andsecurity.

Mainframe computers are powerful computers used primarily by corporate andgovernmental organizations for critical applications, bul2 data processing such as census,industry and consumer statistics, enterprise resource planning, and transaction processing.

7 very large and expensive computer capable of supporting hundreds, or even thousands,of users simultaneously. #n the hierarchy that starts with a simple microprocessor %inwatches, for example' at the bottom and moves to supercomputers at the top, mainframesare -ust below supercomputers.

1ig companies such as 1an2s, #nsurance Companies, Travel and


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8ome more definitions are:

• 7 (owerful Computer$8erver$Technology that supporting thousands of

applications, input$output devices and supporting thousands of userssimultaneously. Today, a Mainframe refers to #1MAs z8eries computers.

• #t is a Style of secured computing designed to continuously run large, mixed

wor2loads at high levels of utilization while meeting userdefined service levelob-ectives.

• 7 mainframe is a large computer system that is used to host the databases,

transaction servers, and applications that re+uire a great degree of security andavailability.

• Mainframe is a large, multiuser computer system designed to handle massive

amounts of input, output and storage. 7 mainframe is usually composed of one or

more powerful C()s connected to many input$output devices, called terminals or to personal computers. Mainframe systems are typically used in businessre+uiring the maintenance of huge databases or simultaneous processing of multiple complex tas2s.

What does the word Mainrame stand or?

The ma-or components of the electronic computers produced in the >34s and early>I4s were mounted on rac2s or frames. #n order to 2eep the lengths of cablesinterconnecting a computerAs components to a minimum %thereby maximize processing

speed', a computerAs central processing unit %C()' and main memory were most oftenhoused together in a single frame, which came to become called the computerAs mainframe.

8o the term Mainframe originated from the early mainframes, as they were housed inenormous, roomsized metal boxes or frames. 6ater the term was used to distinguishhighend commercial machines from less powerful units which were often contained insmaller pac2age.

Today in practice, the term usually refers to computers compatible with the #1M8ystem$I4 line, first introduced in >I3. IBM System z and zEnterprise are #1MAs latest

incarnation. &therwise, systems with similar functionality but not based on the #1M8ystem$I4 are referred to as =servers.= However, =server= and =mainframe= are notsynonymous.

8ome non8ystem$I4compatible systems derived from or compatible with older %preBeb' server technology may also be considered mainframes. These include the1urroughs large systems, the )*#G7C 44$44 series systems, and the pre8ystem$I4 #1M ?44$?444 series. Most largescale computer system architectures were


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firmly established in the >I4s and most large computers were based on architectureestablished during that era up until the advent of Beb servers in the >>4s. %#nterestingly,the first Beb server running anywhere outside 8witzerland ran on an #1M mainframe at8tanford )niversity as early as >>4. 8ee History of the Borld Bide Beb for details.'

Today*s Mainrame

Mainframe development occurred in a series of generations starting in the >34s. #n thosedays, mainframe computers were not -ust the largest computersK they were the onlycomputers and few businesses could afford them.

#n the >?4s and >J4s when almost all computers were big, the term Mainframe wasused to refer to a number of different computer systems. Today most of these are gone,and Mainframe almost always refers to #1M"s z8eries computers.

7s computer technology evolved, mainframe computers became an integral part of

distributed processing systems. #n such systems many smaller computers, such asminicomputers, are lin2ed together in a system controlled by a host computer, often amainframe computer. This is what the reason Mainframe is so called Centralized8ystem!.

The z8eries computers are amongst the largest computers sold today, and they"re used for commercial data processing. 1y commercial data processing we"re really tal2ing aboutdatabase based applicationsK putting a piece of data into a database, loo2ing at it, andta2ing it out.

IBM zEnterprise System is the latest line of #1M mainframes, introduced on Luly ,

44. This comes in two models 9 nterprise Class and 1usiness Class. The znterprisehas a really improved 4Fmar2et share. Bhatever that we discussed and going to discuss on this materials focusonly #1M Mainframes.

http://en.wikipedia.org/wiki/IBM_mainframehttp://en.wikipedia.org/wiki/Market_sharehttp://en.wikipedia.org/wiki/IBM_mainframehttp://en.wikipedia.org/wiki/Market_share


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Why do rely on Mainrames?

Bhenever data processing is a 2ey for any business, we can either go with Distributed

Technology or Midrange Technology or a Mainframes Technology ach has its ownstrengths. 1ut if you don"t bother about Maintenance cost, 8taffing etc., Mainframes isthe 18T technology to drive the Data Processing . Be can understand the reason in thissection.

The main purpose of Mainframes is to run commercial applications of ;ortune 444 businesses and other largescale computing purposes. 1an2ing and insurance businesseswhere enormous amounts of data are processed, typically %at least' millions of records,each day.

,ow Mainrames di-ers rom other technologies?

Though there are a number of reasons or facts, we can combine all these in to a welldefined word 9 TR!ST @es, it is trustworthy technology but what in terms ofDEEEThe answer is RAS "ith S#A$A%&$T' 8calability stands here as numbers!. # meanthe number of processor to be run, the number of peripheral devices to be connected, thenumber of users to be supported, the number of information to be processed and thenumber of application can run. 7ll the above figures are considered as at a time” or atthe given moment!. That is number of application can run at a time!

8ome 2ey points are:

• Mainframes are more powerful than supercomputers because they support moresimultaneous programs. 1ut supercomputers can execute a single program faster than a mainframe.

• Bhile client$server systems are suited for rapid application deployment and

distributed processing, mainframes are efficient at online transactional processing,mass storage, centralized software distribution, and data warehousing

• Mainframes also have tools for monitoring performance of the entire system,

including networ2s and applications not available today on )*#N servers

• Mainframe has come in three tier client$server architecture. The combination of

mainframe horsepower as a server in a client$server distributed architecture resultsin a very effective and efficient system. Mainframe vendors are now providingstandard communications and programming interfaces that ma2e it easy tointegrate mainframes as servers in client$server architecture. )sing mainframes asservers in a client$server distributed architecture provides a more modular systemdesign, and provides the benefits of the client$server technology.


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• )sing mainframes as servers in client$server architecture also enables the

distribution of wor2load between ma-or data centers and provides disaster protection and recovery by bac2ing up large volumes of data at disparatelocations.

• *early all mainframes have the ability to run %or host' multiple operating systems,

and thereby operate as a host of a collective of machines. #n this role, a singlemainframe can replace higherfunctioning hardware services available toconventional servers.

• Mainframes can add or hot swap system capacity without disrupting system

function, with specificity and granularity to a level of sophistication not usuallyavailable with most server solutions.

• Mainframes can handle large volumes of data and (rovide centralized

administration &ffer superior data management capabilities, can handle differenttypes of wor2load, have high data bandwidth, Monitor data integrity and security.

Why to stay on Mainrames? Why not other technologies?

The point that the industries that typically use mainframes %financial$insurance'

will eventually see the cost of maintaining their legacy systems become too high,

and switch to a more modern, distributed, platform. There is, however, a large

cost to converting all these systems over to cheap, for a servers running -ava. *ot -ust the cost of doing it, but the ris2 involved in doing it wrong. #f, hypothetically,

you were to convert a system from mainframe C&1&6 to midrange -ava, and you

messed up a bunch of account values or lost data in any manner, youAd probably

be on the bad end of a class action lawsuit, not to mention potential putative

regulatory action. This is why nobody does that. Commonly system has about /

million lines of C&1&6, and they all %mostly' wor2. 6i2e they say, =#f it ainAt

bro2e, donAt fix it.=

The cost of running additional wor2load on distributed servers goes up linearly

which increases cost per unit of wor2 as the wor2load grows.


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The cost of running incremental wor2load on the mainframe goes down as the

total wor2load grows and Customers have learned that mainframes running high

throughput wor2loads are the most costefficient platform.

The Total Cost of 8torage is typically three times more in 5istributed

nvironments.

Mainrames strengths

"%S or Mainrames

Reliability(

The mainframes systemAs hardware components have extensive selfchec2ing and

selfrecovery capabilities.

The systemAs software reliability is a result of extensive testing and the ability to

ma2e +uic2 updates for detected problems.

#1M boasts that you can bet all your money on 7 Mainframe, when it comes to


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Serviceability(

The system can determine 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.

This term also implies welldefined units of replacement, either hardware or

software.

;aults can be detected early on a Mainframe Computer. Bhen some components

fail, some of #1MAs systems can automatically call the #1M 8ervice center.


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Bhen you hit a certain wor2load the larger servers or mainframe environments

are more energy efficient on an Renergy used perS unit of wor2 basis than multiple

servers wor2ing together. Be too2 a loo2 at the energy used for the same

wor2load when run on distributed fourway )nix servers and on a z> mainframe

machine. The energy consumption of the z 8ervers was ten times less.

7nd this is the main reason for which #1M is ran2ed *o+ ,reen #ompany in

the world.

#ontinuing compatibility(

Many Mainframes applications are written decades ago and which are still

running, and few may be written yesterday" The ability of an application to wor2

in the system or its ability to wor2 with other devices or programs is called

compatibility.

Mainframes effectively allow downward compatibility with flawless execution of

software applications in new hardware configuration.

*o other computer architecture can claim as much continuous, evolutionary

improvement, while maintaining compatibility with previous releases.


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Why .usiness should preer Mainrames? / 0alues 1Mainrames

Some facts about mainframe .//0-.//1 Statistics2(

>3 F of the ;ortune 444 enterprises use #M8 &riginally written in >IJ to support *787"s 7pollo program

3 of the world"s top 3 1an2s, of the top 3 )8


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4o" can mainframes help you cope "ith planned and unplanned outages3

)ni+ue mainframe clustering technology for maximum uptime


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MT1; %Mean Time 1etween ;ailure' for servers lies between 4 9 /4 years.

Who uses Mainrames daily?

Lust about everyone is using, has used a mainframe computer at one point or another. #f you ever used an automated teller machine %7TM' to interact with your ban2 account,you used a mainframe. 7 ban2ing institution could use a mainframe to host the databaseof its customer accounts, for which transactions can be submitted from any of thousandsof 7TM locations worldwide.

Today, mainframe computers play a central role in the daily operations of most of theworld"s largest corporations. #n ban2ing, finance, health care, insurance, utilities,government, and a multitude of other public and private enterprises, the mainframecomputer continues to be the foundation of modern business.

8o whenever a business application is accessed through a web browser, there is often amainframe computer performing crucial functions behind the scene.!

Many of today"s busiest websites store their production databases on a mainframe host. *ew mainframe hardware and software products are ideal for web transactions becausethey are designed to allow huge numbers of users and applications to rapidly andsimultaneously access the same data #ithout interfering with each other. This security,scalability, and reliability are critical to the efficient and secure operation of contemporary information processing.

%usinesses today rely on the mainframe to(

(erform largescale transaction processing %thousands of transactions per second'

8upport thousands of users and application programs concurrently accessing

numerous resources

Manage terabytes of information in databases

Handle largebandwidth communication

4o" come such an old technology standstill3

)n2nown to many, mainframe machines are still here to stay. Bhile we wor2 onBindows and )*#N systems, the mainframe still is 2ing.

6ong before there were des2tops and servers, the only computers used for business weremainframes with #1M leading the pac2. Mainframes used to occupy a large area in a building. 1ut with modern technology, they are now becoming smaller in their footprint.There had been a lot of changes to mainframe technologies that they can also be used as


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8ervers in a web enabled world and hence the mainframe computer continues to be thefoundation of modern business.

#n the >>4As, the word was =the mainframe is dead=. Two decades later, this proves to bewrong. How does the mainframe fit in the modern world of computingEEE The fact is

organizations have built their businesses around mainframe code and it will be too ris2yfor them to convert their core applications to something new. #1M has ta2en advantage of this and is extending the capabilities of their older compilers. 7 chec2 of their programming manuals shows that (6$ can now wor2 with NM6. C&1&6 can be used asan ob-ect oriented language.

Technologies from (rogress and #1M can convert the dump green screens to web servicesthat can be accessed by web applications. These also convert these green screens intoHTM6 pages that can ma2e them loo2 li2e they were served from modern day webapplications. These technologies also allow a mainframe program to access an externalweb service. 1y using technologies li2e this, the mainframe can be leveraged for its

strengths. Bith cloud computing on the horizon, a study conducted for C7 Technologiesshow that ?>F of uropean organizations believe the mainframe will be integral to their implementation of this technology.

8o...@oung developers who want to wor2 in large organizations will benefit by pic2ing upsome 2nowledge of how mainframes wor2. #t may be old and it may be a totally differentworld compared to Bindows and 6inux machines. 1ut things seem to indicate that it ishere to stay.


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,ow Mainrame wor+s?

&n the hardware behalf Mainframe is made up of thousands, maybe millions, C()s andthey all wor2 in parallel. &n the software behalf a Mainframe computer wor2s by ma2ing

replacing dozens of virtual machines thus emulating hundreds of smaller servers runningdifferent operating systems reducing the management and administrative cost whileimproving the scalability and reliability.

To put simply, a Mainframe is a central computer, or a server. 7ll terminals, which arevery basic (Cs will connect to the mainframe and it will do all the wor2 and the (C actsmore or less li2e a remote monitor$2eyboard$mouse. These (C could be any type of computers either a 8erver or Micro or Mini computers.

Who are all must #e needed to run M4

Mainframe systems are designed to be used by huge numbers of people. 1ecause of thelarge number of users, applications running on the system, and the sophistication andcomplexity of the system software that supports the users and applications, a variety of roles are needed except users to operate and support the mainframe system. )nli2e personal computer we need a group of people to maintain or support Mainframes while itruns, mostly all the day.

Who5s "ho in the Mainframe "orld3

The following group of people are needed to run Mainframe:

System programmer: The system programmer installs, customizes, and maintains theoperating system or subsystems, and also installs or upgrades products that run on thesystem. The system programmer must be s2illed at debugging problems with systemsoftware. They are needed to maintain Middle#are such as database managementsystems, online transaction processing systems, and web servers. Middleware is asoftware layer ! between the operating system and the user or user application. #tsupplies ma-or functions that are not provided by the operating system. Middleware products such as 51, C#C8, and #M8Q can be as complex as the operating systemitself.

System administrator( The person who maintains the critical business data that resides

on the mainframe. 8ystem administrators perform more of the daytoday tas2s related tomaintaining the critical business data that resides on the mainframe, while the system programmer focuses on maintaining the system itself. 7lthough system programmer expertise lies mainly in the mainframe hardware and software areas, systemadministrators are more li2ely to have experience with the applications.


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Common system administrator tas2s can include:

#nstalling software

7dding and deleting users and maintaining user profiles

Maintaining security resource access lists

Managing storage devices and printers

Managing networ2s and connectivity

Monitoring system performance

Application Developer( They design, build, test, and deliver mainframe applications for the company"s users and customers. 7pplication 5eveloper is not only responsible tocreate new applications but also for maintaining and enhancing the company"s existing

mainframe applications. 7s mainframe installations still create new programs withC&1&6 or (6$#, languages such as Lava and C$CVV applications, developers are neededto maintain the code at all the levels.

System operator( The person who monitors and controls %/$?' the operation of themainframe hardware and software. The operator 8tarts and 8tops system tas2s, subsystems such as transaction processing systems,

database systems, and the operating system itself. (erform an orderly shutdown and startup of the system and its wor2loads, when it

is re+uired. Monitors the system consoles for unusual conditions

Bor2s with the system programming and production control staff to ensure thehealth and normal operation of the systems.

7s applications are added to the mainframe, the system operator is given with run boo2 %8&( 9 8tandard &perations (rocedure' of instructions to ensure that they run smoothly.


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Production control analyst( The person who ensures that batch wor2loads run tocompletion without error or delay. Most of Mainframe installations run interactive onlinewor2loads followed by a batch -obs that run %sometimes after the prime shift' when theonline systems are not running. The (roduction control staffs understand that the use of Bellstructured rules and procedures to control changes, strength of the Mainframe

environment and prevent outages.

Mainframe ;endors( 7 number of vendor roles are commonplace in the mainframe.Most of Mainframe computers are sold by #1M, and the operating systems and primaryonline systems are also provided by #1M, most vendor contacts are only a #1Memployees.

However, independent software vendor %#8G' products are also used in the #1MMainframe environment, and customers use original e+uipment manufacturer %&M'hardware, such as dis2 and tape storage devices, as well.

Typical vendor roles are: #ustomer )ngineer( The #1M hardware maintenance person is often referred to

as the customer engineer %C' who provides onsite support for hardware devices.The C usually wor2s directly with the operations teams if hardware fails or if new hardware is being installed.

Soft"are support( #1M has a centralized 8upport Center that provides entitled

and extracharge support for software defects or usage assistance. They validatethe application product errors and give us a solution.

Mainrame Wor+loads ( .atch 5 1nline

Bhatever you spea2 on Mainframes, the wor2load lies either 1atch processing or &nline processing. 8o mainframe wor2loads always fall into one of two categories: batch processing, or online transaction processing, including Bebbased applications.

%atch Processing(

To 2eep it simple, 1atch (rocessing is running of -obs %a basic M; wor2load 9 Bhateverwor2 is done on Mainframe is called jobs” ' on the mainframe #ithout user interaction.Be will see batch processing in detail.

7 2ey advantage of mainframe systems is the ability to process terabytes of data fromhighspeed storage devices and produce valuable output. ;or example, mainframesystems ma2e it possible for ban2s and other financial institutions to produce endof+uarter processing in an acceptable time frame %runtime' when such reporting isnecessary to clients %such as +uarterly stoc2 statements or pension statements' or to thegovernment %financial results'. Bith mainframe systems, even retail stores can generateand consolidate nightly sales reports for review by regional sales managers.


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The applications %programs' that produce these statements are batch applications are processed on the mainframe without user interaction. 7 batch -ob is submitted on thecomputer, which reads and processes data in bul2 %perhaps terabytes of data'. 7 batch -obmay be part of a group of batch -obs that need to process in se$uence %one after one' to

create a desired outcome. This outcome may be output such as client billing statements.

#haracteristics of %atch processes(

7 scheduled batch process can consist of the execution of hundreds or thousands

of individual -obs %programs' in a preestablished se+uence. Hence, during batch

processing, multiple types of wor2 can be generated. Consolidated information,

such as profitability of investment funds, scheduled database bac2ups, processing

of daily orders, and updating of inventories, are common examples. 6arge amounts of input data are processed and stored %perhaps terabytes or more'

that is, large numbers of records are accessed, and a large volume of output is

produced.

#mmediate response time is usually *&T a re+uirement. However, batch -obs

often must complete within a batch "indo",! %within 4 hours or within 3 pm'

as prescribed by a service level agreement %867'. 5uring its run, the online

activity would be very minimal.

*ow in the modern Mainframes, batch window is getting shrin2, and batch -obs

are now often designed to run concurrently with online transactions with minimal

resource contention.

Bhile batch processing is possible on distributed systems, it is not as commonplace as it

is on mainframes, because distributed systems often lac2:

8ufficient data storage

7vailable processor capacity, or cycles

8ysplex wide management%logically merge more than one system' of system

resources and -ob scheduling


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When and "here the %atch processing is needed3

#t is used when there is a lot of transactions$hits on a master file and the response neededis not immediate, usually it may be until the end of the day or wee2 or even a month. 7good example would be payroll processing, where nearly every master file record will be

affected. The data is collected over a period of time, then input and verified by cler2s%verified means input by someone else and then both inputs are compared by computer'and processed centrally. 7fter the output is produced, and is usually printed media such as pay slips or invoices, although this is changing with the advent of the web.


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software. The way data is to be displayed on the terminal has to be mapped. The mapping

process depends on the interactive system used.

Typically, mainframes serve a vast number of transaction systems as it can support anunpredictable number of concurrent users and transaction types. Most transactions areexecuted in short time periods %fractions of a second in some cases'.

&nline transactions usually have the following characteristics:

7 small amount of input data, a few stored records accessed and processed, and a

small amount of data as output

#mmediate response time, usually less than one second

6arge numbers of users involved in large numbers of transactions


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Criticality o a Mainrames* "untime

So without Mainrames this may happen)66

@our airplane might not land safely %air traffic control'

@our 7TM would not give you money %ban2s all over the world'

@ou could not buy something online %transaction processing'

Trains could not run everywhere %virtual 6inux servers'

Hospitals could not access patient records %(atient Management'

@our ;edx $)(8 pac2age would not shipE %shipping and trac2ing of shipments'

The #nternet would not wor2.


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!ntroduction to !.M Mainrames

!.M Mainrames

#1M mainframes are large computer systems produced by #1M from >3 to the present.5uring the >I4s and >?4s, the term mainframe computer was almost synonymous with#1M products due to their mar2et share. Current mainframes in #1MAs line of businesscomputers are developments of the basic design of the #1M 8ystem$I4.

!ntroduction to !.M Mainrames ( ,ardware / ServerModels

!.M System789:7ll that changed with the announcement of the 8ystem$I4 %8$I4' in 7pril, >I/. The

8ystem$I4 was a single series of compatible models for both commercial and scientificuse. The number =I4= suggested a =I4 degree,= or =allaround= computer system.8ystem$I4 incorporated features which had previously been present on only either thecommercial line %such as decimal arithmetic and byte addressing' or the technical line%such as floating point arithmetic'. 8ome of the arithmetic units and addressing featureswere optional on some models of the 8ystem$I4. However, models were upwardcompatible and most were also downward compatible. The 8ystem$I4 was also the firstcomputer in wide use to include dedicated hardware provisions for the use of operatingsystems. 7mong these were supervisor and application mode programs and instructions,as well as builtin memory protection facilities. Hardware memory protection was provided to protect the operating system from the user programs %tas2s' and the user tas2s

from each other. The new machine also had a larger address space than the older mainframes, / bits vs. a typical J bits.

The smaller models in the 8ystem$I4 line %e.g. the I4$4' were intended to replace the/44 series while providing an easier upgrade path to the larger I4s. To smooth thetransition from second generation to the new line, #1M used the I4As microprogrammingcapability to emulate the more popular older models. Thus I4$4s with this added costfeature could run /4 programs and the larger I4$I3s could run ?4>/ programs. To runold programs, the I4 had to be halted and restarted in emulation mode. Many customers2ept using their old software and one of the features of the later 8ystem$?4 was theability to switch to emulation mode and bac2 under operating system control. &perating

systems for the 8ystem$I4 family included &8$I4 %with (C(, M;T, and MGT',1&8$I4, T&8$I4, and 5&8$I4.

The 8ystem$I4 later evolved into the 8ystem$?4, the 8ystem$>4, and the I/bit z8eries and 8ystem z machines. 8ystem$?4 introduced virtual memory capabilities in allmodels other than the very first 8ystem$?4 modelsK the &8$G8 variant of &8$I4 M;T,the &8$G8 %8G8' variant of &8$I4 MGT, and the 5&8$G8 variant of 5&8$I4 wereintroduced to use the virtual memory capabilities, followed by MG8, which, unli2e the

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earlier virtualmemory operating systems, ran separate programs in separate addressspaces, rather than running all programs in a single virtual address space. The virtualmemory capabilities also allowed the system to support virtual machinesK the GM$?4 hypervisor would run one or more virtual machines running either standard 8ystem$I4or 8ystem$?4 operating systems or the singleuser Conversational Monitor 8ystem

%CM8'. 7 timesharing GM system could run multiple virtual machines, one per user,with each virtual machine running an instance of CM8.

1S78;:

&8$>4 is the #1M operating system most commonly installed on its 8$>4 lineof mainframe server . #t is an evolved and newly renamed version of MG8 %MultipleGirtual 8torage', #1MAs longtime, robust mainframe operating system. 1y whatever name, MG8 has been said to be the operating system that 2eeps the world going. The payroll, accounts receivable, transaction processing, database management, and other programs critical to the worldAs largest businesses are usually run on an MG8 system.

7lthough MG8 tends to be associated with a monolithic, centrallycontrolled informationsystem, #1M has in recent years repositioned it as a =large server= in a networ2orienteddistributed environment that would tend to use a tier application model.

8ince MG8 represents a certain epoch and culture in the history of computing and sincemany older MG8 systems still operate, the term =MG8= will probably continue to be usedfor some time. 8ince &8$>4 also comes with )*#N user and programming interfaces built in, it can be used as both an MG8 system and a )*#N system at the same time.&8$>4 %and earlier MG8' systems run older applications developed using Common1usiness &riented 6anguage and, for transaction programs, Customer #nformationControl 8ystem. &lder application programs written in (6$# and ;ormula Translation are

still running. &lder applications use the Girtual access method for file managementand Girtual Telecommunications 7ccess Method for telecommunication with users. Themost common program environment today uses the C and CVV languages. 51 is #1MAs primary. Lava applications can be developed and run under &8$>4As )*#N environment.;or additional information about ma-or components of &8$>4, see MG8. &ther #1Moperating systems for their larger computers include or have included: the Transaction(rocessing ;acility %T(;', used in some ma-or airline reservation systems, and virtualmachine, an operating system designed to serve many interactive users at the same time.

!.M System <

#1M 8ystem z, or earlier #1M e8erver z8eries, is a brand name designated by #1M to allits mainframe computers. #n 444, #1M rebranded the existing 8ystem$>4 to #1Me8erver z8eries with the depicted in #1MAs red trademar2ed symbol, but because nospecific machine names were changed for 8ystem$>4, the z8eries in common use refersonly to one generation of mainframes, starting with z>44.

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new boo2 and removes the old one without interruption to running applications. %*otethat #1M mainframe processors have a reported /4 year MT1;.' 8imilar designredundancies exist in memory, #$&, power, cooling, and other subsystems. 7ll thesefeatures exist at the hardware and microcode level, without special application programming. The same concepts can extend to coupled frames separated by up to 44

2ilometers in a 0eographically 5ispersed (arallel 8ysplex when z$&8 is used.8ystem z servers are used by #1M customers for businesscritical installations in mediumand large organizations which need very high availability, where scheduled andunscheduled downtime costs are high, and at traditional mainframe shops such as ban2sand insurance companies which already have mainframe applications at the center of their business processes. ;or such organizations which have to consider a very high pricefor system failures and service outages, 8ystem z machines may provide a lower totalcost of ownership than other platforms, especially when running a variety of businesscritical applications concurrently %socalled mixed wor2load'. &verall, mainframes li2e8ystem z are mostly used in government, financial services, retail, and manufacturingindustries.

Today=s &>atest' systems (


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znterprise systems consists of components

C(C 9 Can be either znterprise >I %z>I' or znterprise / %z/'

znterprise 1ladeCenter xtension %z1N'

znterprise )nified I'Wthe industryAs fastest and most scalable enterprise system. Tosupport a wor2load optimized system, the z>I can scale up %over 3,444 M#(8 in asingle footprint', scale out %J4 configurable cores' and scale within %specialty engines,cryptographic processors, hypervisors' executing in an environmentally friendlyfootprint. 7nd the z>I is designed to wor2 together with system software, middlewareand storage to be the most robust and cost effective data server. The z>I offers anindustry standard (C#e #$& drawer for ;#C&* and &87xpress multimode and single

mode fiber optic environments for increased capacity, infrastructure bandwidth, andreliability.

;or the first time since >>3, the z>I is an #1M mainframe that allows for li+uidcooling. Customers have the option of purchasing the mainframe with a watercooledheat exchanger

The z>I offers a total of >I cores running at an astonishing 3. 0Hz, and delivering upto /4 percent improvement in performance per core and up to I4 percent increase in totalcapacity for z$&8P, z$GMP, and 6inux on 8ystem zP wor2loads compared to its predecessor, the z4Q C. The z>I has up to J4 configurable cores for client use. The

cores can be configured as general purpose processors %C(s', #ntegrated ;acilities for 6inux %#;6s', 8ystem z 7pplication 7ssist (rocessors %z77(s', 8ystem z #ntegrated#nformation (rocessors %z##(s', additional 8ystem 7ssist (rocessors %87(s', #nternalCoupling ;acilities %#C;s' or used as additional spares.

This design, with increased capacity and number of available processor cores per server,and reduced energy usage and floor space, ma2es the z>I a perfect fit for largescale


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consolidation. The virtualization capabilities can support up to /? distributed servers on asingle core, up to thousands on a single system.


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=)nterprise ++> 8++>2

7t the core of the znterprise 8ystem for both midsized and small enterprises is the nextgeneration mainframeWthe znterprise / %z/'Woffering new levels of freedom anda whole new world of capabilities for a broader set of businesses.

)ni+ue hybrid architecture enables integration and centralized management of Mainframe, (&B


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Mainrame Server Models &chronological order'

The older 8$>4 #1M mainframe servers are considered history since support for the last8$>4 compatible version of z$&8 %.3' was dropped on March , 44?.

#1M introduced two entries for each server models since #1M 8ystem z is introduced.They are:

%usiness #lass %#2

)nterprise #lass )#2

The 1usiness Class %1C' could be said to be intended for small to midrange enterprisecomputing, and delivers an entry point with granular scalability and a wide range of capacity settings to grow with the wor2load.

The 1C shares many of the characteristics and processing traits of its larger sibling , thenterprise Class %C'. This model provides granular scalability and capacity settings on amuch larger scale and is intended to satisfy highend processing re+uirements. 7s a result,the C has a larger frame to house the extensive capacity that supports greater processingre+uirements.

44 %4I/ series', for larger customers %444'

zJ44 %4II series', entrylevel, less powerful variant of the z>44 %44'

z>>4 %4J/ series', successor to larger z>44 models %44'

zJ>4 %4JI series', successor to the zJ44 and smaller z>44 models %44/'

System nterprise Class %4>/ series', introduced in 443 initially as z>4>,

beginning the new 8ystem z> line

z> 1usiness Class %4>I series', successor to the zJ>4 and smallest z>>4 models

%44I'

System ? series', introduced on ;ebruary I, 44J

z4 1usiness Class %4>J series', introduced on &ctober , 44J

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I %J? series', introduced on Luly , 44

znterprise / %JJ series', introduced on Luly I, 4

ach Mainframe has different number of sub models for its specifications. xample, theMainframes industryAs fastest and most scalable and flexible enterprise server >I hasM3, M, M/>, MII and MJ4. ach model differs from its specifications.

z>I comes as a nterprise class for a lager businesses and at the same time z/ comesas 1usiness class for a smaller organizations or businesses.

The z>I offers a total of >I cores running at an astonishing 3. 0Hz, and delivering up

to /4 percent improvement in performance per core and up to I4 percent increase in totalcapacity for z$&8P, z$GMP, and 6inux on 8ystem zP wor2loads compared to its predecessor, the z4Q C. The z>I has up to J4 configurable cores for client use. Thecores can be configured as general purpose processors %C(s', #ntegrated ;acilities for 6inux %#;6s', 8ystem z 7pplication 7ssist (rocessors %z77(s', 8ystem z #ntegrated#nformation (rocessors %z##(s', additional 8ystem 7ssist (rocessors %87(s', #nternalCoupling ;acilities %#C;s' or used as additional spares.

This design, with increased capacity and number of available processor cores per server,and reduced energy usage and floor space, ma2es the z>I a perfect fit for largescaleconsolidation. The virtualization capabilities can support up to /? distributed servers on a

single core, up to thousands on a single system.

)nterprise #lass

The znterprise >I is available in five hardware models: M3, M, M/>, MII andMJ4. The model number is based on the number of cores available for customerAswor2load %additional cores are usually installed and used for redundancy and other purposes'

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%usiness #lass

The znterprise / is available in two models the M43 and the M4. #ntroduced in Luly,

4, this system is designed to extend the benefits of the znterprise >I system to the

midrange business segment. 6i2e the z>I, the z/ is fully compatible with the z1N

and the )


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!ntro to !.M Mainrames ,ardware

CPC &Central Processing Comple3'

7n #1M mainframe that has two or more central processors %C(s' that share memory. #tis the collection of processors, memory and #$& subsystems manufactured with a singleserial number, typically all contained in one cabinet. The z8eries C(C contains from 3 to4 processors.

7 C(C that can be physically partitioned to form two operating processor complexes is2nown as Multiprocessor.

Channel Su#system

The heart of moving data into and out of a mainframe host is the channel subsystem, or C88. The C88 is, from a central processor standpoint, independent of the processors of the mainframe host itself. This means that input$output %#$&' within a mainframe host can be done asynchronously.

Bhen an #$& operation is re+uired, the C88 is passed the re+uest from the main processor. Bhile awaiting completion of an #$& re+uest, the main processor is able tocontinue processing other wor2. This is a critical re+uirement in a system designed tohandle massive numbers of concurrent transactions.

7ll 6(7


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8C&* and ;#C&* channels connect to only one device or one port on a switch.

Most modern mainframes use switches between the channels and the control

units. The switches may be connected to several systems, sharing the control units

and some or all of its #$& devices across all the systems.

CH(#5 addresses are two hexadecimal digits.

Multiple partitions can sometimes share CH(#5s. Bhether this is possible

depends on the nature of the control units used through the CH(#5s. #n general,

CH(#5s used for dis2s can be shared.

7n #$& subsystem layer exists between the operating systems in partitions %or in

the basic machine if partitions are not used' and the CH(#5s.

Many users still refer to these as =addresses= although the device numbers are arbitrarynumbers between xA4444A and xA;;;;A. TodayAs mainframes have two layers of #$&address translations between the real #$& elements and the operating system software. Thesecond layer was added to ma2e migration to newer systems easier.

Modern control units, especially for dis2s, often have multiple channel %or switch'connections and multiple connections to their devices. They can handle multiple data

transfers at the same time on the multiple channels. ach device will have a unit control bloc2 %)C1' in each z$&8 image.

D%SD

7 5785, or 5irect 7ccess 8torage 5is2, is a type of storage device that is connecteddirectly to a user"s computer rather than being connected to the networ2. 1ecause manytypes of storage device connect directly to a user"s computer, the term 5785! mayapply to a variety of different devicesK however, a 5785 is typically a storage device thatcontains a significant amount of memory and a relatively low access time. ;or example,des2top servers and external hard drives are good examples of 5785s, although flash

drives and 85 cards can be considered 5785s as well.


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Magnetic Tape

Magnetic tape is the best storage medium for data and contains most of the data that isstored in the data processing environment. Magnetic tape is made by ta2ing a plastic tapeand bonding a layer of magnetic material on the tape. 7 spot on the tape could be

magnetized one way and would represent a one. Magnetized in the other direction, thespot would represent a zero. 0roups of these spots can be combined to represent one byte. 0roups of bytes are a physical bloc2 on the tape.

The performance of the tape subsystem is measured by the throughput of the subsystemin megabytes or gigabytes per second. The throughput depends on certain architecturalfactors as well as certain factors decided by the application programmer.

The number of active tape drives and channel paths( The number of channel pathslimits the number of drives transferring data.

%uffering in the control unit tape cache2( #f the control unit does not have to wait for the tape to complete an action, the throughput of the subsystem will be better.

The speed of the tape over the read@"rite heads: The faster the tape moves, the faster data can be transferred.

#hannel speed( The speed of the channel can operate an upper limit on the data transfer rate. #f the channel operates at three megabytes per second, then the tape drive canoperate at any speed to and including three megabytes per second.

#hannel utili=ation( 8elector mode channels can operate up to 44 percent channel busy

without degradation of the entire channel. The total transfer of all the bloc2s from thetape may be longer because the #$& is waiting for the channel to get started.

>par

6ogical partition %6(7


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An $par has the follo"ing properties(

ach 6( is a set of physical resources %C(), storage, and channels' controlled by

-ust one independent image of an operating system, such as z$&8, 6inux, C;CC,

z$GM, or G8. @ou can have up to I4 6(s in a server.

ach 6( is defined through #&C($HC5. ;or example, the #&C(


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M;S Multiple ;irtual Storage2

MG8 is an evolutionary system. #t has evolved over the architecture of 1atch (rocessingconcept. This means it ta2es a -ob from the -ob +ueue, and executes it. MG8 is one of the

most complex software written so far. (erformance and ease of use are the two factorsthat influenced the evolution of the MG8.

MG8 is an operating system from #1M that continues to run on many of #1M"smainframe and large server computers. MG8 has been said to be the operating systemthat 2eeps the world going and the same could be said of its successor systems, &8$>4and z$&8. The payroll, accounts receivable, transaction processing, databasemanagement, and other programs critical to the worldAs largest businesses are usually runon an MG8 or successor system. 7lthough MG8 has often been seen as a monolithic,centrallycontrolled information system, #1M has in recent years repositioned it %andsuccessor systems' as a =large server= in a networ2oriented distributed environment,

using a tier application model.

The Girtual 8torage in MG8 refers to the use of virtual memory in the operating system.Girtual storage or memory allows a program to have access to the maximum amount of memory in a system even though this memory is actually being shared among more thanone application program. The operating system translates the programAs virtual addressinto the real physical memory address where the data is actually located. The Multiple inMG8 indicates that a separate virtual memory is maintained for each of multiple tas2 partitions.

=@4, which in turn followed a string of MG8 versions.R*1 S 6i2e &8$>4, z$&8 combines a number of formerly separate, related products,some of which are still optional. z$&8 offers the attributes of modern operating systems but also retains much of the functionality originating in the >I4s and each subse+uentdecade that is still found in daily use %bac2ward compatibility is one of z$&8As centraldesign philosophies'. z$&8 was first introduced in &ctober, 444.

z$&8 is the computer operating system for #1MAs z8eries >44 %z>44' line of large%mainframe' servers. z$&8 is a renamed and upgraded version of &8$>4, which in turn

evolved from the MG8 operating system. #1MAs renamed servers and operating systemsreflect a strategy to realign its products more closely with the #nternet and its own e business initiatives.

z$&8 is described as an extremely scalable and secure highperformance operating system based on the I/bit z$7rchitecture. 6i2e its predecessor, &8$>4, z$&8 lays claim to beinghighly reliable for running missioncritical applications. The operating system supportsBeb and Lavabased applications.


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Characteristics o Mainrame 1perating Systems

Multiprogramming and Multiprocessing(

$&8 is capable of multiprogramming, or executing many programs concurrently, and of

multiprocessing, which is the simultaneous operation of two or more processors thatshare the various hardware resources.

The earliest operating systems were used to control singleuser computer systems. #nthose days, the operating system would read in one -ob, find the data and devices the -obneeded, let the -ob run to completion, and then read in another -ob. #n contrast, thecomputer systems that z$&8 manages are capable of multiprogramming, or executingmany programs concurrently. Bith multiprogramming, when a -ob cannot use the processor, the system can suspend, or interrupt, the -ob, freeing the processor to wor2 onanother -ob.

z$&8 ma2es multiprogramming possible by capturing and saving all the relevantinformation about the interrupted program before allowing another program to execute.Bhen the interrupted program is ready to begin executing again, it can resume execution -ust where it left off. Multiprogramming allows z$&8 to run thousands of programssimultaneously for users who might be wor2ing on different pro-ects at different physicallocations around the world.

z$&8 can also perform multiprocessing, which is the simultaneous operation of two or more processors that share the various hardware resources, such as memory and externaldis2 storage devices.

The techni+ues of multiprogramming and multiprocessing ma2e z$&8 ideally suited for processing wor2loads that re+uire many input$output %#$&' operations. Typical mainframewor2loads include longrunning applications that write updates to millions of records in adatabase, and online applications for thousands of interactive users at any given time.1y way of contrast, consider the operating system that might be used for a singleuser computer system. 8uch an operating system would need to execute programs on behalf of one user only. #n the case of a personal computer %(C', for example, the entire resourcesof the machine are often at the disposal of one user.

Many users running many separate programs means that, along with large amounts of complex hardware, z$&8 needs large amounts of memory to ensure suitable system

performance. 6arge companies run sophisticated business applications that access largedatabases and industrystrength middleware products. 8uch applications re+uire theoperating system to protect privacy among users, as well as enable the sharing of databases and software services.

Thus, multiprogramming, multiprocessing, and the need for a large amount of memorymean that z$&8 must provide function beyond simple, singleuser applications. The


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related concepts listed below explain the attributes that enable z$&8 to manage complexcomputer configurations.

Time Sharing(

#n batch system, the user cannot interact with the -ob when it is being executed. #t meansthat all possible problems must be anticipated before hand as the user cannot ma2ecorrections during execution. #t becomes very difficult when a program has to go throughmany phases such as compilation, lin2ing etc. #t may be difficult to define what to do if a particular phase tails. 7nother problem is the debugging of a program. 7ll debugging isstatic. The only information to find out is why the program is giving incorrect output atvarious stages of execution.

Time sharing was introduced to ma2e computer systems more interactive. C() is themost important resource that is shared. ach -ob gets C() for a small amount of time.

Bhen the allotted time period for a -ob is used, the next -ob in line is allocated C().

The switching between -obs occurs very fre+uently. #t allows the user to interact with, the -ob as it is running. &perating system should enable the user to interact with -obs that areexecuting. The communication usually occurs via 2eyboard. The user gets a prompt toenter commands. The user must 2now the status of the -ob in order to enter relevantcommands. The output of a -ob is usually presented on a monitor.

0enerally, the commands given by the user ta2e very little time to execute. The controlreturns to command line after finishing a command. #t displays a prompt to indicate thatthe system is ready to execute another command. 5&8 and )nix are examples of such of system.

%atch processing

Bor2 is processed in units called -obs. 7 -ob may cause one or more programs to executein se+uence. &ne of the problems that arise when batch processing is used is managinghow wor2 flows through the system. To manage this in the multiuser system, the Lobntry 8ubsystem %L8' processes each userAs -ob in an orderly fashion.

Spooling(%8imultaneous (eripheral &perations &nline'

The overlapping of lowspeed operations with normal processing. 8pooling originatedwith mainframes in order to optimize slow operations such as reading cards and printing.Card input was read onto dis2 and printer output was stored on dis2. #n that way, the business data processing was performed at high speed, receiving input from dis2 andsending output to dis2. 8ubse+uently, spooling is used to buffer data for the printer aswell as remote batch terminals.


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The spooling of documents for printing and batch -ob re+uests still goes on in mainframecomputers where many users share a pool of resources. &n personal computers, your print -obs %for example, a Beb page you want to print' are spooled to an output file onhard dis2 if your printer is already printing another file.


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,!ST1"@ %ND 201>AT!1N 14 M%!N4"%M2S1P2"%T!NB S@ST2M

What is an


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)volution of Mainframe 33 and 0M*77 #$& in >3I for use on its own #1M computersK and in >I1urroughs Corporation released MC( and 0eneral lectric introduced 0C&8, in bothcases for use by their customers. #n fact the first operating systems for #1M computerswere written by #1M customers who did not wish to have their very expensive machines%XM in the mid>34s' sitting idle while operators set up -obs manually, and so theywanted a mechanism for maintaining a +ueue of -obs.The operating systems developed in that era were not compatible with 6ower end andhigher end systems, which in turn increased the production cost for both hardware andsoftware, which was affecting the sales as customers did not have an easy option for upgrading the system. 8o in >I/ the company announced System@B:/, a new range of computers which all used the same peripherals and most of which could run the same

programs.

System@B:/ C


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M;T- Multiprogramming "ith a ;ariable number of TasEs

• #t treated all memory not used by the operating system as a single pool from which

contiguous =regions= could be allocated as re+uired by an indefinite number of

simultaneous application programs.

•This scheme was more flexible than M;TAs and in principle used memory moreefficiently, but was liable to fragmentation after a while one could find that, although

there was enough spare memory in total to run a program, it was divided into separate

chun2s none of which was large enough.

• There was a need to eradicate the problem of memory shortage thus #1M came up with

the concept of virtual storage. Bhich allowed programs to re+uest address spaces larger

than physical memory.

• The original implementations had a single virtual address space, shared by all -obs, 8o


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M;S@B0/ is a generic term for all versions of MG8 operating system prior to MG8$N7.The 8ystem$?4 architecture, at the time MG8 was released, supported only /bit virtualaddresses, so the MG8$?4 operating system architecture is based on a /bit address.1ecause of this /bit address length, programs running under MG8$?4 are each givenI megabytes of contiguous virtual storage.

M;S@?A, or Multiple ;irtual Storage@)xtended Architecture, was a version of MG8that supported the ?4N7 architecture, which expanded addresses from / bits to bits, providing a gigabyte addressable memory area. #t also supported a /bit legacyaddressing mode for older /bit applications %i.e. those that stored a /bit address in thelower / bits of a bit word and utilized the upper J bits of that word for other purposes'.

4 was introduced in late >>3 in an effort, led by the late


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eatures of 8@


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Mainrame Su#systems and 4acilities

TS< and &SP(

T8& %Time 8haring &ption' is an MG8 component that lets terminal users access MG8facilities. T8& does this by treating each terminal user as a -ob. Bhen you logon to T8&,T8& creates a LC6 stream and submits to L8$L8 for processing. ach T8& user isgiven a uni+ue address space and can allocate data sets and invo2e programs -ust as a batch -ob can. The T8& commands reside in [email protected]#1 and are located into the private area of the T8& userAs address space as re+uired. The Terminal Monitor (rogram%TM(' is a program that accepts and interprets commands and causes an appropriatecommand processor to be scheduled and executed.

The T8& environment has both MG8 and T8& user address spaces and MG8 and T8&user data sets. The system address spaces are Master 8cheduler, L8, 17TCH, GT7Mand T8&. T8& user spaces are created as users 6&0&*.

TS


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;igure below shows the #8(; menu structure

8uch tools include

1rowse for viewing data sets, (artitioned 5ata 8et %(58' members, and )nix

8ystem 8ervices files.

dit for editing data sets, (58 members, and )nix 8ystem 8ervices files.

)tilities for performing data manipulation operations, such as:

5ata 8et 6ist which allows the user to list and manipulate %copy, move, rename,

print, catalog, delete, etc.' files %termed =data sets= in the z$&8 environment'.

Member 6ist for similar manipulations of members of (58s.

8earch facilities for finding modules or text within members or data sets.

Compare facilities for comparing members or data sets.

6ibrary Management, including promoting and demoting program modules.


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Storage Management Subsystem SMS2

The 8torage Management 8ubsystem, commonly referred to as 8M8, is an #1M productthat became available with MG8$87. The purpose of 8M8 is to provide the user withsystemmanaged data, intended to simplify user interface for allocating and maintaining

data, provide the user with a logical view of data, separated from the actual physicaldevice characteristics and to provide centralized control of dis2 storage.

(lacing the data set under 8M8 control has certain benefits. 5is2 allocation for new datasets is directed to the most suitable group of dis2 volumes under centralized dis2storageadministration control. The user does not determine which volumes will be used whereas8M8 does this. The management of a data set after it is created of archive, retention etc.,is also under centralized administration control. The LC6 is also simplified.

;irtual Telecommunication Access Method

MG8 uses the most powerful access method viz., Girtual Telecommunications 7ccessMethod %GT7M', a part of the comprehensive telecommunications product called 8*7,which stands for 8ystem *etwor2 7rchitecture.

GT7M is considered to be a subsystem because it runs in its own address space. GT7Mis able to provide centralized control over all of the terminal devices attached to an MG8system. ach GT7M terminal device is allocated to the GT7M address spaces,communicate with those terminal devices indirectly. They issue re+uests to GT7M, whichin turn services the re+uest for the appropriate terminal.

There are two re+uired data sets that control how GT7M operates: [email protected]#1

contains the GT7M load modules and user defined tables and exit [email protected] contains the definition statement and start options for theGT7M.GT7M applications that must be defined to GT7M with an 7((6 statement. Thisallows networ2 resources to communicate with that application through GT7M. 7n7((6 definition must be coded for each application program.

#S

C#C8 %Customer #nformation Control 8ystem' is a transaction subsystem that handlesinteractions between terminal users and online application programs. C#C8 is asubsystem of GT7M, and so any C#C8 system must be defined to GT7M. 7 connection

between the user terminal and C#C8 is automatically established when either C#C8 or GT7M is started. nd users identify themselves to C#C8 by signing on to begin an onlinesession.

C#C8 is an online transaction processing %&6T(' program from #1M that, together withthe C&1&6 programming language, has formed over the past several decades the mostcommon set of tools for building customer transaction applications in the world of largeenterprise mainframe computing. 7 great number of the legacy applications still in use

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are C&1&6$C#C8 applications. )sing the application programming interface %7(#' provided by C#C8, a programmer can write programs that communicate with online usersand read from or write to customer and other records %orders, inventory figures, customer data, and so forth' in a database %usually referred to as =data sets=' using C#C8 facilitiesrather than #1MAs access methods directly. 6i2e other transaction managers, C#C8 can

ensure that transactions are completed and, if not, undo partly completed transactions sothat the integrity of data records is maintained.

#1M mar2ets or supports a C#C8 product for &8$>4, )*#N, and #ntel (C operatingsystems. 8ome of #1MAs customers use #1MAs Transaction 8erver to handle ebusinesstransactions from #nternet users and forward these to a mainframe server that accesses anexisting C#C8 order and inventory database.

&MS

#M8 #1MAs main database before 51, and still highly valued by its customers. The

2ey characteristic of #M8 is that record schemas are arranged in a =tree= structure. ;or example, if a particular structure has a =teacher= record =root= with several =student=record =branches,= the same structure cannot have a student record root with severalteacher record branches that must be done with a separate structure. 7s a result, datastores with this type of manytomany relationship are much larger with #M8, and performance in typical database tas2s is slower. However, for runthebusinessapplications that do not typically involve manytomany relationships, #M8 is superior,and therefore many businesscritical mainframe applications from the >I4s and >?4scontinue to use #M8. #1M has periodically updated #M8 to handle new environmentssuch as the Beb.

#M8 %#nformation Management 8ystem' has two components: 56$# and 5ataCommunications. The 56$# component of #M8 allow users set up and maintain complexhierarchical databases that can be processed by application programs run as batch -obs. #f the optional 5ata Communications component of #M8 %#M8 5C' is used, interactiveapplication programs can be coded that use #M8 databases and communicate withterminals.

6i2e C#C8, #M8 5C implements its own multiprogramming that is transparent to MG8.#M8 5C multiprogramming is more li2e MG8 multiprogramming than C#C8multiprogramming, however. The #M8 control region in its own address space schedulesapplication programs for execution in dependant regions %also in separate address

spaces'. The control region also manages communication between the application programs, databases, and terminals.

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D%.

51 is a family of relational database management system %


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%inding

1efore a program can be executed, a process called binding must be performed. 1indingestablishes a lin2age between the application program and the 51 data it accesses.1inding process involves only the 51


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#$&ST

C6#8T %Command 6ist' %pronounced =C6ist=' is a procedural programming languagefor T8& in MG8 systems. #t originated in &8$I4


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7


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What is a dataset3

The term data set refers to a file that contains one or more records. The record is the basicunit of information used by a program running on z$&8 or in simple words its e+uivalent

of a file in other operating systems, such as Mac &8, Bindows

7ny named group of records is called a data set. 5ata sets can hold information such asmedical records or insurance records, to be used by a program running on the system.5ata sets are also used to store information needed by applications or the operatingsystem itself, such as source programs, macro libraries, or system variables or parameters. ;or data sets that contain readable text, you can print them or display themon a console %many data sets contain load modules or other binary data that is not really printable'. 5ata sets can be cataloged, which permits the data set to be referred to byname without specifying where it is stored.

;SAM - ;irtual Storage Access Method

G87M stands for Girtual 8torage 7ccess Method. The G87M is a method used for managing files in mainframe system. That is in other words G87M is a data managementsystem used in mainframe systems and this was introduced by #1M. G87M also 2nownas Girtual 8torage 7ccess Method is an access method for #1MAs mainframe operatingsystem MG8.

;SAM Structure(

The management of data ta2es place as records in G87M system and it is allowed for

G87M to be of any length as per the ends of user. The G87M supports fixed as well asvariable length records. These records are placed in bloc2s which are termed as Control#ntervals and these Control #ntervals are measured in bytes. The Control #ntervals arefurther placed as Control 7reas which is still of larger size.

Types of ;SAM datasets(

The datasets of G87M are generally referred as clusters and there are four types ofG87M datasets based on the way the records are stored and accessed which are given below:

• ntry 8e+uenced 5ata 8et %858'

•Uey 8e+uenced 5ata 8et %U858'

• 6inear 5ata 8et %658'

•


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dataset. This method of G87M helps to maintain records in se+uential order. The 858cluster has one component viz. data component.

7s we have seen before the records in 858 datasets are accessed by specifying the physical location and so the records in 858 cluster are stored in the order in which they

are entered into the dataset maintaining their physical entry or location. The record isreferenced by the relative byte address also termed as


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#n contrast to the other two methods li2e U858 and 858 the

Basic MF Introduction

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