Introduction - Mainframes

INTRODUCTION

1.     Mainframe is a computer or a machine which can perform millions of instructions at a time.

2.     Mainframe computer is implemented by IBM in 1950’s.

3.     They came into existence in 1960’s.

4.     Mainframe computers are famous in the form of servers.

5.     Mainframe servers are somewhat special than general servers.

6.     In Mainframe server environment for every application we can expect 99.9% accuracy.

7.     Mainframe is 2^nd highest in computer category after super computer because performance levels of mainframe servers are very high.

8.     Mainframes can store 1000’s of terabytes (TB) of data into the databases.

9.     Mainframes can process 1000’s of transactions per second.

10.            Mainframes can process mixed workloads of data.

11.            In mainframe server environment we are having two types of processes. They are

1.     Online Processing

2.     Batch Processing

Online Processing :

Online Processing is also called as Interactive Processing where use interaction is required. In online processing for every response from the system user have to give a reply.

Example: ATM

Batch Processing:

Batch is a collection of one or more jobs. All jobs are equal to programs. In batch processing once batch is started it will be controlled by the system itself (only one time interaction is enough).

12. For mainframe server we are having a specially designed storage components that is DASD.

                   DASD - Direct Access Storage Device

13. DASD is a physical storage for a mainframe computer.

14. DASD is a collection of volumes which will store the data physically in it.

15. For mainframe server we are also having specially designed OS i.e.

      MVS

                   MVS – Multiple Virtual Storage

16. MVS was the 1^st OS used for mainframe.

17. MVS was implemented in 1960’s as a commercial version.

MVS EVOLUTION:

MVS having different versions as follows …..

1. MVS/360

2. MVS/370

3. MVS/390

4. Z/OS

1. MVS/360

·        Introduced in 1970

·        24 bit architecture

·        16 MB addressing capacity

·        Single Processor

·        MVS/360 is like DOS environment

2. MVS/370

·        Introduced in 1970

·        24 bit architecture

·        Introduced Virtual Storage

·        Multiple C.P.U (Max 2)

·        Increase I/O computing

·        Somewhat faster and flexible than MVS/360

3. MVS/360-XA

·        IN 1980 Extended Architecture

·        31 Bit architecture

·        2 GB addressing capacity

·        Multiple C.P.U (Max 6)

4. MVS/390

·        Introduced in 1994

·        It is a latest version and many functions are added

1. Unix functions were added

2. C, C++ compilers were added

3. Graphical User Interface (GUI) is added

·        It is very flexible than previous versions and also MIPS and CMOS technologies were implemented

5. Z/OS

·        Implemented in 2001

·        It is very faster than all previous versions

·        IN Z/OS CMOS,MIPS were fully implemented

·        System Z provides 99.9% availability environment for the applications running on it

·        Z/OS extends all properties of MVS/390 for the flexible displacement of new applications

·        In Z/OS we are also having some versions as follows…..

a.     Z/VM     -        Virtual Machine

b.     Z/VSE    -        Virtual Storage Extended

c.      Z/TPF    -        Transactional Processing Facility

Usage Areas:

Mainframes are mainly used in following areas……….

·        Banking

·        Finance

·        Insurance

·        Health Care

·        Government Sectors like Railways, Census and Scientific Apps

Characteristics of Mainframes:

1. Reliability:

          If any unwanted circumstances occurred in the system we can easily rectify.

2. Availability:

a.     If any system failure occurs we can easily rectify without affecting other operational systems

b.     In mainframe server it provides 99.9% availability environment (continuous support)

3. Servicabiliity

          We can recover the failed components easily by using some software and hardware elements while impacting as little of the other operational systems

4. Security:

a.     These are very secured servers in the environment

b.     It controls the unauthorized access and protects the data

5. Scalability:

          It is an ability to retain the performance levels of a computer bhy adding some memory units to it

6. Compatibility:

a.     It is an ability to run in specific OS

b.     It is flexible for any environment

Features of Mainframes:

1. Multi-Programming:

          Executing one or more application programs at a time is called Multi-Programming

2. Multi-Tasking:

          Executing one or more task at a time

3. Virtual Storage:

a.     It is a temporary storage we can process the task firstly.

b.     Virtual Storage is created from main storage only but it is not permanent because that is only for temporary usage

c.      Virtual Storage is very less memory and also called as “buffer storage”

4. Batch Processing:

a.     Batch is a collection of one or more jobs

b.     In batch processing all ‘batches’ will be processed in the units called ‘jobs’

c.      In batch process user communication is optional

5. Spooling:

a.     It is the method of placing inputs into a batch and printing the outputs is called “Spooling”

Spool – Simultaneous Peripheral Outputs Online

b.     In spooling along with main processor we have an Input-Output Processor

c.      By having Input-Output Processor we can reduce the manual loading time

d.     Input-Output Processor will control both Input and Output sections

e.      Input-Output Processor will prepare data for input jobs and also prints the previous batch results

f.       By running main and Input-Output Processor simultaneously we can process number of jobs per second

6. Time Sharing:

a.     It allows multiple numbers of users to interactively work with the system

b.     All users must contain a valid authentication while communicating with mainframe server

Drawback:

          Mainframe is cost effective

Advantages:

a.     Mainframes are very secured server

b.     They are good in performance

c.      They can store large amount of data

d.     It is used by FORTUNE 1000 MNC’s in the world

Mainframe Jobs:

In mainframe server environment we are having various roles as follows….

1. Application Programmer:

 He will develop the projects in COBOL based on client requirement

2. System Programmer:

 All software and hardware elements will be controlled by system programmer

3. System Administrator:

All machinery operations will be organized by Admin

System Administrator will also provide security for the data in mainframe server

4. System Operator:

 The main work of operator is to start and stop the sub-systems

5. Production Control Analyst:

 He analyses the online regions like CICS….. etc