new ppt

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VERSION 2.0VERSION 2.033rdrd July 2000 July 2000

2MVS

Day-wise Schedule

Details of the Sessions

Day 1 Session 1 Computing Environment -Key Concepts

(Theory) & terminology, Typical IBM MF site.

IBM Operating Systems

IBM families of OS

- IBM Hardware

- MVS Implementation

Session 2 Demo on ISPF (Lab) Familiarizing with various options of TSO

& ISPF Editor

Day 2 Session 3 MVS Functions (Theory) Data Management Overview

- Job Management Overview

MVS Tools Overview

Session 4 Assignments (Lab) ISPF editor & TSO

3MVS

COMPUTING ENVIRONMENT

KEY CONCEPTS & TERMINOLOGY

4MVS

Command Issue Mode How a user (programmer / end-user) interacts with the computer

E.g. To edit a program, to execute a program On-line Mode - Using Terminal Batch Mode - Using Punched Cards or JCL

Command Execution Mode Foreground - Terminal is locked while the command is being executed Background - Terminal is free while the command is being executed

Command Processing

5MVS

How Business applications are executed On-line

– End User performs business functions– Application programs work interactively with End User– Execution is in foreground mode– Database is immediately updated to reflect the changes– Typically used for transaction processing, queries, master

updates functions

Data Processing

6MVS

Batch

– Application programs are executed in background mode

– Periodic business functions are executed automatically

– “As and when” business functions are triggered by End User

– Operations department is responsible for monitoring the

execution

– A command file is created to execute these functions

– One command file may consist of multiple programs / system

utilities

– Typically used for bulk transaction processing, report printing ,

periodic processing (e.g. invoice generation, payroll calculation)

Data Processing

7MVS

Resource Sharing Multiple Users compete for computer resources at

the same time At any given point in time only one user can have

control of the resources What should be the basis of sharing?

1. First come first served?2. Priority based?3. Who so ever can grab it - Law of Jungle?4. Equal - Democratically?5. Need based?

Usually combination of 2 and 4 is used i.e. all are equal but some are more equal!!!!!

Time Sharing

8MVS

Time Slice– Each user is given control of resources for a pre-defined

period - time slice– The control is passed on to next in queue user at the end of

time slice (even if first user’s work is incomplete)– If the user requires I/O before the time slice is over, the

control is handed over to the next user (since CPU cannot do anything until I/O is complete)

Time Sharing

9MVS

Priority

– Each user / function is assigned a priority level

– The higher priority users are serviced first in a round robin

fashion

– Only if the higher priority users are in “wait” state for I/O

completion the users in the lower priority are serviced

Time Sharing typically refers to sharing of resources in an

interactive processing mode

Time Sharing

10MVS

Why Multi-programming?– The program has CPU based and Non-CPU based

instructions – CPU is kept waiting during the non-CPU based instructions

execution

E.g. I/O operations (Disk, Terminal, Printer)– This results in wastage of CPU time - a precious resource– Multi-programming results in better CPU utilization

Multi-programming

11MVS

How Does it Work?– Multiple programs are kept “ready” for execution– CPU can execute only one program at any given point in

time– If the currently executing program requires I/O, it is put in a

“wait” state– Another program is immediately taken for execution– On completion of I/O the program again becomes “ready”

for execution

This results in an illusion that multiple programs are being executed simultaneously, hence multiprogramming.

Multi-programming

12MVS

Multi-programming Overheads– Program Queue Management– Program Status Management– Context Switching during Changeover– Multiple programs must be in main memory– Management of Common Resource Sharing (e.g. Printer)

It is critical to determine optimum level of Multi-programming to maintain certain service level.

Relevance of Multi-programming– Multi-programming is applicable even for single user system– Multi-programming is a must for multi-user system

Multi-programming

13MVS

There are multiple CPUs (processors) in one machine These work together under single operating system Each CPU executes a separate program O/S assigns programs to each CPU Essentially CPU is treated as an allocable device!!!!!

Multi-processing

14MVS

Why Spooling?

– Multiple programs may need same printer at the same time

– May result in intermixing of output

– Exclusive access to a program will hold other programs

– Printer is much slower, results in longer “wait” state

How it is Implemented?

– Output to printer is intercepted and written to a disk i.e. “spooled”

– On completion of program “spooled” output is queued for Printing

– This queue is processed by O/S print routine

– The O/S print routine is multi-programmed along with application programs

Spooling

15MVS

Why Virtual Storage– Required to enable execution of programs with are larger than the main

memory size

What is Virtual Storage– Technique to simulate large amount of main storage– Reality is main storage is much less– E.g. Real main storage is 16MB but virtual storage is 2GB

How Virtual Storage is Implemented– Program executable code is generated assuming virtual storage size– Only part of the program is loaded in main memory– Address translation mechanism is used to map virtual address to actual

address– Feasible because only the instruction currently being executed and the

corresponding data need to be in the main storage

Virtual Storage

16MVS

Advantages of Virtual Storage– Main memory can be shared by multiple programs– Enables effective use of the limited main storage

Overheads of Virtual Storage

– Address mapping– Keeping track of what is in memory and what is not – Data/Instructions need to be “brought in” main memory as

an when required– “Remove” from main memory what is not currently required

(to make room for instructions of other program)– Memory Management

Virtual Storage

17MVS

Business Environment Large Local or Global Operations or Both User Community in Hundreds Almost non-stop operations (weekly maintenance window of about 1/2

day) Large Volumes of Data / High Volumes of Transactions Hundreds of Applications / Mission Critical Applications

Computing Environment - Typical IBM MF Site

18MVS

Processing Environment– On-line during prime time (might mean 24 hours for global operations)

– Batch during non-prime time (wrt local time) of 12 - 15 hours

Software Environment– Variety of Databases / OLTP packages

– EDI Processing

– Two Tier Database Architecture - C/S and Central

Hardware Environment– Multiple Machines - Networked Together

– Multiple Processors for Each Machine

– Huge Number of Data Storage Devices - Disks and Tapes


19MVS

Support Environment– Huge IT Departments– Application Programming Staff

Development Maintenance / Support

– DBAs– Operations Multiple Data Centers to Manage Batch

Processing– System Programmers for;

- O/S

- Database Packages

- OLTP Packages– Network Support Staff


20MVS

IBM Families of Operating Systems

DOS - Disk Operating System

For Small System/360

DOS/VSE(Virtual Storage Extended)

VM/CMS - Virtual MachineConversation Monitor System

Simulates more than one computer system on single real machine

Supports both DOS and OS

• Migrating from Dos to OS is a major change

• VM is not very popular • Today most of the sites use

MVS

OS - Operating System

For Full range System/360 MVS(Multiple Virtual Storage)

21MVS

1995 MVS/ESA 5.2.2

1993 MVS/OPEN EDITION(POSIX)

1990 SYSTEM 390

1988 MVS/ESA 16 TB

1981 MVS/XA 2 GB (31-bit)

1974 OS/VS2R2(MVS) 16 MB (24-bit)

1972 OS/VS1 OS/VS2R1(SVS)16 MB

1970 SYSTEM 370

1966 OS/MFT OS/MVT 3 MB

1966 PRIMARY CONTROL PROGRAM (PCP)

MVS Evolution

22MVS

PCP Primary Control Program

Basically a PrimerIntroduction of JCL-(JOB Control Language)(Became obsolete 1n 1969

No MultiprogrammingNo PriorityNo SpoolingVery unreliable

1966 MFT Multi-programming with Fixed number of Tasks

Limited multi-programmingSmall improvementover PCP

Storage allocated as per requirement (region)No. of Jobs depends upon storage req. and availability

1967/68 MVT Multi-programming with Variable number of Tasks

Reliable Comprehensive featuresPredecessor of MVS

Fixed Number of PartitionsOne Job per PartitionFixed Partition Size

Operating Systems for System/360

1965

MVS Evolution

23MVS

Major Handicaps– Limited and inefficient spooling– No Virtual Storage

Utilities to Overcome these Handicaps– HASP - Houston Automatic Spooling Priority

Developed unofficially (self initiative) by IBM employees Distributed free to MVT/MFT users Became very popular Eventually owned and supported by IBM

MVS Evolution

24MVS

ASP - Attached Support Processor Developed (officially) by IBM Intended for MVT Several mainframes can work together under single O/S (predecessor of

multi-processing?) Provided better spooling capability Relatively less takers

MVS Evolution

25MVS

System 370

Announced in early 70s Supported Virtual Storage New Operating Systems OS/VS were introduced

– OS/VS1 (Virtual System 1) - adopted from MFT– OS/VS2 (Virtual System 2)

Version SVS - Single Virtual Storage

- adopted from MVT (1972) Version MVS - Multiple Virtual Storage

- Completely Rewritten (1974)

HASP and ASP were migrated to OS/VS2 under the names JES2 and JES3

MVS and its derivatives are the mainstay of IBM O/S now

MVS Evolution

26MVS

1974 OS MVS/SP1 Multiple Virtual Storage/VS2 System/37024 bit addressability

Greater reliability / integrity / performanceVirtual storage limitation of 16MB - A serious handicap for CICS

1983

Processors :308x, 3090, 4381

1988

MVS MVS/SP3 Multiple Virtual Storage/ESA Enterprise Systems Architecture ESA/370

Processors :ES/3090 E and S Models and later4381 Models 90E, 92E, 93E and later

1990 MVS MVS/SP4 Multiple Virtual Storage/ESA Enterprise Systems Architecture ESA/390

Processors :ES/9000, ES/3090-9000TES/3090 J Models

32 bit addressabilityVirtual storage of 2GBIncreased maximum number of channels and Devices

Virtual storage of 16 Terra Bytes

Virtual storage of 16 Terra Bytes

MVS/XA

MVS Evolution

27MVS

The Von Neumann Computing Model

Most common model for computing systems

Prepared by John Von Neumann in year 1940

Instruction 1

Instruction 2

Instruction 3

Instruction 4

---- ----- ----

Register

Instructions are executed one at a time sequentially

28MVS

Operating System Considerations

a) Process Management

Problem :- According to Jon Von Neumann model only one instruction gets executed at a time. What will happen if that instruction is waiting for I/O. In this case CPU time is wasted.

Solution :-

This gave rise to multiprogramming

P1

P2

P3

READ

File

Hard Disk Memory

Main Memory

Auxiliary Device

1) executing instruction

2) I/O operation

3) Now this will get executed

29MVS

b) Memory Management

Problem :- Any thing that is to be executed, must be in memory. (memory limitation)Solution :- 1. Place task in real memory

2. Place task in virtual memory

1. Real memory implementation :

- code & data are in real memory - size of code & data limited by size of installed memory - good performance, low overhead - possible wastage of memory


30MVS

Memory Management (Contd ..)

2. Virtual memory implementation :– based on assumption for a task, not all code & data is

needed in real memory all the time– implemented on a combination of real plus auxiliary

storage– operating system takes responsibility of bringing rest

part of tasks in real memory when required.


31MVS

P1

P2

P3

P1

DATA

Virtual Memory

swapped out Perform I/O operation

swapped in

Real Memory(Only part of program that requires main memory will be in the mainmemory)

P2

OS


Advantage : code and data size independent of the real memory

32MVS

c) Input-output Management

Problem :- Application should not worry about device characteristics. I/O device speed is 100 times slower than CPU.

Solution : Let all I/O be handled by a specialized system-I/O Subsystem


33MVS

c) Input-output Management ( Contd.. )

2) I/O operation

P1

P2

P3

P1

Virtual Memory

Real Memory Auxiliary Device

swapped out

swapped in I/OSubsystem

OS

How it is to be done is decided byI/O subsystem

Tells What to do

P2


File

34MVS

System 370 I/O Architecture

Channel 0

Channel 1

Channel 2

Channel 3

Channel 4

Channel 5

Channel 6

Channel 7

Main StorageCPU

35MVS


Processor CPUs Main Memory MaximumChannels

4381 1 or 2 4 - 6 MB 18

3084 4 32-128 MB 48

3090 6 64-512 MB 128

ES/9000 4-8 2048 MB 256

Typical Processor Configuration

36MVS

STORAGE

CP CP

Channels

Devices

Channels– Provide paths between the processor & I/O devices– 3090 processors can have a maximum of128

channels– A channel itself is a computer & executes I/O

instructions called channel commands– I/O devices are connected to channels through an

intermediate device called “Control Unit”.– Each channel can have up to 8 control units.


37MVS

Control Unit :-• These are DASD units, can be connected to common

control unit, called “String Controller”.• String Controller can be connected to a channel

directly or indirectly• A control unit called “Storage Control” connects string

controllers to a channel.

DASD unit

channel connection

storage control

string controller1

string controller1

(1 - 128)(1 - 8)

32

32


38MVS

How do today’s PC and medium sized IBM MF compare?

IBM Hardware

Characteristics PC (Pentium100)

Main Frame(4381)

Processor Speed 16-32 MB 32 MB

Main Memory 16-32 MB 32 MB

Individual DiskStorage

1.2 GB 946 MB

Monitor SVGA/Graphics

Character baseddumb terminal

39MVS

Where does the power of IBM MF come from?– Multiple processors with partitioning capability– Cache memory and expandable memory– Multi-user / Multi-programming Support– Batch and on-line processing support– Local and remote terminal support– High number of devices– Strong data management capability

IBM Hardware

40MVS

Cache Memory– High speed memory buffer (faster than main memory)– Operates between CPU and main memory– Used to store frequently accessed storage locations

(instructions)– Usually available on all processors

Expanded Memory– Supplements main memory– Not directly available to application program– Not directly accessible by CPU– Implemented using high speed disk– Usually available with higher-end machines

Key Terminology

41MVS

Processor Resource / System Manager (PR/SM)• Used to control Multi-processor Configurations• Allows division of multi-processors in partitions - LPAR• Each partition functions as independent system• Enables fault tolerance implementation by designating Primary

and Secondary Partitions• Secondary partition takes over automatically if primary fails• Allows reconfiguration of I/O channel to partitions

Key Terminology

42MVS

Channels– Device Management Concept - Unique to IBM– Provides access path between CPU and I/O devices

(DMA)– Upto eight control units can be connected to one channel– Upto eight I/O devices can be connected to one control

unit– A channel is a small computer in itself with a set of

instructions (Channel commands)– Channel controls the I/O device operations independent

of CPU– Cannel processing can overlap CPU processing -

improved performance

Key Terminology

43MVS

Channel - I/O Device Connectivity– Parallel architecture i.e. all bits of a byte are transmitted

simultaneously– Information transfer is in unit of two bytes– Sixteen data wires and additional control wires are required– Maximum length of 120 meters (400 feet)– Data speed of 4.5mbps– Use of copper results in heavy, expensive cabling

ESCON - Enterprise System Connection– Announced in 1990– Uses fiber optic– Results in reduced size and weight– Length limit extended to approximately 42Km (26 miles)– Faster data speed (17mbps)

Key Terminology

44MVS

Unit Record Devices - Each record is a single physical unit– Card Devices (now obsolete) : Readers / Punches / Reader and

Punches– Printer

• Impact Printers - 600 to 2000 LPM• Non-Impact Printers - 3800 sub-system, 20,000 LPM

– Built-in control units for each device– Directly attached to channel

Magnetic Tape– High volume storage– Sequential processing– Normally used as back-up device– Also used for physical transfer of data– 4 to 8 tape drives are connected to one control unit

I/O Devices

45MVS

DASD - Direct Access Storage Device– IBM’s official name for Disk– Non-removable - offers better reliability and are faster– Each unit is called as disk pack or Volume– Each pack has multiple surfaces– Each surface has multiple tracks– Same track no. of all surfaces together constitute a Cylinder– DASD capacity ranges from 100 MB (3330) to 8514MB

(3390/9)– A group of DASDs of same type are connected together to

form a String and are connected to a string controller– Multiple string controller are connected to a storage

controller– Storage controller is connected to channel

I/O Devices

46MVS

3990 Storage Controller– Can connect 2 strings of 32 each 3390 model DASDs

(totally 64 DASDs– Consists of high speed cache storage (32MB to 1024MB)– Data is buffered using cache– Frequently accessed data is stored in Cache - improved

performance– Supports more than 4 channel connection to processor

• Enables several simultaneous disk operations

I/O Devices

47MVS

Data Communication equipment lets an installation create a data communication network that lets users at local terminals & remote terminals to access computer system

Data Communication Equipment

48MVS

Allows local and remote terminals access to the computer systems

Components of data communication– Host Computer - System/370 processor– Communications Controller - Attached to the channel

• Devices (terminals and printers) are connected to the terminal controller (also known as cluster controller)

• Terminal controller is connected to communications controller

• Terminal Controller managing Local terminals / printers can be connected directly to the channel


49MVS

– Modems and telecommunication lines (telephone line, Satellite Link)

• Remote terminals / printers are connected to terminal controller (at local site)

• Terminal controller is connected to modem• Modem is connected to telecommunications line• At the receiving end telecommunications line is

connected to modem• Modem is connected to communication controller


50MVS

3270 Information Display System– Sub-system of terminals, printers and controllers connected

to Host computer– Locally through communications controller or directly to

channel– Remotely through communications controller, modem and

telecommunications line– A typical 3270 terminal controller (3274) controls upto 32

terminals / printers– Emulator programs (Shine Link, Erma Link) allow

computers (typically PCs) to mimic 3270 devices– These are useful since they allow upload / download of data

between MF and PC


51MVS

System/370 processor

channelHost System

communication controller

modem modem

modem

terminal controller

terminalprinter

modem

terminal controller

terminalprinter

TelecommunicationLines

Remote System Remote System


52MVS

At the center of the network is the host system, a system/370 processor

The control unit that attaches to the host system’s channels is called a communication controller– it manages the communication function– necessary to connect remote terminal system– via modems and telecommunication lines

A modem is a device that translates digital signals from the computer equipment at the sending end into audio signal that are transmitted over a telecommunication line, which can be telephone line, a satellite link or some other type of connection

At the receiving end of the line, another modem converts those audio signals back into digital signal


53MVS

Why is grasping IBM difficult?– User interface is poor

• Non-intuitive• Unfriendly and Formidable

– Ancient terminology (e.g. Card, Punch queue) which is irrelevant now

– Different terminology (e.g. DASD, DATA SET)– Too many options / parameters– Too many terms / acronyms – Variety of software results in site specific variations

Often Asked Questions About IBM

54MVS

Why is IBM so Popular– Sturdy and Secure HW/SW– Downward compatibility (does not make application SW

obsolete)– Excellent customer support– Variety of software (Databases, OLTP packages) - IBM

and Third Party– Market Leader

• First in DBMS, First in OLTP, first in PC!!!!• First to develop a chess playing computer that beat world champion


55MVS

The old legend : Nobody got fired for buying IBM Future of IBM (is there any?)

– Large existing application base will need support– Downsizing will need knowledge of current

application/platform– Dual skills will be much in demand– Not all applications are suitable for downsizing - many will

remain on MF– MF will be increasingly used as back-end server– New applications (data warehousing type) will be developed

on MF– Multi-tier architecture will become common

Bottom Line : It is too soon to herald death of IBM MF


56MVS

Characteristics Features Of MVS

1] VS : The use of virtual storage increases the number of storage locations available to hold programs and data

2] MULTIPROGRAMMING : Multiprogramming simply reclaims the CPU during idle periods to let other programs execute

3] SPOOLING : To provide shared access to printer devices, spooling is used

4] BATCH PROCESSING : When batch processing is used, work is processed in units called “Jobs”. A job may cause one or more programs to be executed in sequence. Batch jobs get collectively processed by the system

57MVS

5] TIMESHARING : In this system, each user has access to the system through a terminal device. Instead of submitting jobs that are scheduled for later execution, the user enters commands that are processed immediately.

Time sharing is also called as Online Processing because it lets users interact directly with the computer.

Characteristics Features Of MVS

58MVS

MVS Terminology

Address Space

¨ An address space is simply the complete range of addresses and as a result, the number of storage locations; that can be accessed by the computer.

¨ An address space is a group of digits that identify a physical location in main storage

¨ In MVS an address space has 24-bit positions i.e. 16MB addressability.

¨ MVS allows each programmer to use all 16MB address space, even though real storage includes only, for example 4MB physical locations.

59MVS

Address Space (Contd..)• In MVS, references in the program address space are not

associated with a particular real storage location. They remain reference to a particular piece of information called Virtual Addresses. They become real only when assigned to a physical location.

• When the program is ready to execute the system, using a system/370 hardware feature called Dynamic Address Translation(DAT), maps the virtual addresses in the program to the real storage addresses.

• By doing this, MVS can make the program address space larger than the number of physical location available in real storage.

MVS Terminology

60MVS

MVS

It uses real storage to simulate several address spaces, each of which is independent of the others

IIAddress Space I III

0 0 0

RealStorage

AuxiliaryStorage

MVS Terminology

61MVS

¨ Auxiliary storage and real storage are used in combination to simulate several virtual storage address space

¨ Each batch job or TSO user is given its own address space

¨ Various factors such as the speed of the processor and the amount of real storage installed effectively limit the number of address spaces than can be simulated.

¨ To provide for the larger virtual storage, MVS treats DASD as an extension of real storage

¨ Only one address space can be in control of CPU

MVS Terminology

62MVS

Paging To enable the movement of the parts of a program executing

in virtual storage between real storage and auxiliary storage, the MVS system breaks real storage, virtual storage & Auxiliary storage into blocks.

- A block of Real Storage is a Frame

- A block of Virtual Storage is a Page

- A block of Auxiliary storage is a Slot A page, a frame and a slot are all the same size each is a 4K

byte An active virtual storage page resides in a real storage frame,

an inactive virtual storage page resides in an auxiliary storage slot

MVS Terminology

63MVS

Paging

Moving pages between real storage frames and auxiliary storage slots is called PAGING

Virtual Storage

Page

Frame Slot

Real Storage Auxiliary Storage

PAGING

MVS Terminology

64MVS

Demand Paging

Assume that DAT encounters an invalid page table entry during address translation, indicating that a page is required that is not in a real storage frame. To resolve this Page Fault, the system must locate an available real storage frame to map the required page(page-in). If there is no available frame, an assigned frame must be freed. To free a frame, the system moves its contents to a auxiliary storage. This movement is called a Page-Out.

System performs page-out only when the contents of the frame have changed since the page was brought into real storage.

Once a frame is located for the required page, the contents of the page are moved from auxiliary storage to real storage. This movement is called as Page-In.

MVS Terminology

65MVS

Demand Paging (Contd ..)

The process of bringing a page from auxiliary storage to real storage in response to a Page Fault is called DEMAND PAGING

MVS tries to avoid the time consuming process of demand paging by keeping an adequate supply of available real storage frames constantly on hand. Swapping is one means of ensuring this adequate supply. Page stealing is another.

MVS Terminology

66MVS

Swapping

Swapping is the movement of an entire address space between Virtual storage & Auxiliary storage.

It is one of the several methods MVS employs to balance system workload, as well as to ensure that an adequate supply of available real storage frames is maintained.

Address space that are swapped in are active, having pages in real storage frames & pages in auxiliary storage slots.

Address spaces that are swapped out are inactive; the address space resides on auxiliary storage and cannot execute until it it is swapped in.

MVS Terminology

67MVS

Page Stealing

If there are not enough 4K frames available then frames which are not referenced for long time will get thrown out and written to the auxiliary storage. So now those 4K frames are free. This is known as Page Stealing.

MVS Terminology

68MVS

The paging process is managed by several components of MVS. The 3 major one are :

- Real Storage Manager (RSM)

- Auxiliary Storage Manager(ASM)

- Virtual Storage Manager (VSM)

RSM

- manages real storage

- directs movements of pages among real and auxiliary

- builds segment & page table

MVS Terminology

69MVS

ASM – keeps track of the contents of the page dataset and

swap dataset– page dataset contain virtual pages that are currently

occupying a real storage frame.– Swap dataset contain the LSQA pages of swapped

out address space.

VSM– controls allocation/deallocation of virtual storage– maintain storage use information for Storage

Management Facility (SMF)

MVS Terminology

70MVS

Virtual Storage Layout

Local System Queue Area (LSQA)

Scheduler Work Area (SWA)

User Region

System Region

System Queue Area (SQA)

Pageable Link Pack Area (PLPA)

Common Service Area (CSA)

User’s Private AddressSpace

Nucleus

CommonArea

PrivateArea

SystemArea

Each Virtual Storage Address Space consists of a System Area, a Private Area and a Common Area.

71MVS

System Area

It contains the nucleus load module, page frame table entries. Data blocks for system libraries and so many other things

Nucleus and other contents of the System Area make up the resident part of the MVS system control program

Its contents are mapped one for one into real storage frames at initialization time.

The size of System Area does not change once it is initialized


72MVS

Common Area

It contains parts of the system control program, control

blocks, tables and data areas

The basic parts of the Common Area are :

System Queue Area (SQA)

Pageable Link Pack Area (PLPA)

Common Service Area (CSA)


73MVS

System Queue Area

– contains tables and queues relating to the entire system

– the contents of SQA depends on an installation’s

configuration & job requirement

– It is allocated from the top of the virtual storage in 64K

segments, a minimum of 3 segments are allocated

during system initialization.

– Allocated SQA space is both non-swappable and non-

pageable


74MVS

Pageable Link Pack Area

- Contains svc routines, access methods, other system programs, and selected user programs.

- It is pageable

- Because the modules in PLPA are shared by all users, all program modules in PLPA must be reentrant and read-only

- PLPA space is allocated in 4K block directly below SQA.

- The size of PLPA is determined by the number of modules included

- Once the size is set, PLPA does not expand


75MVS

Common Service Area

Contains pageable system and user data areas.

It is addressable by all active virtual storage address space

and shared by all swapped-in users.

Virtual storage for CSA is allocated in 4K pages directly

below PLPA.


76MVS

Private Area The Private Area is made up of :

- Local System Queue Area(LSQA)

- Scheduler Work Area(SWA)

- Subpools 229/230

- System Region

- User RegionThe user region is the space within Private Area that is

available for running the user’s program

Local System Queue Area

- LSQA contains tables and queues that are unique to a particular address space


77MVS

Private Area (Contd ..)

Scheduler Work Area

- SWA contain control blocks that exist from task initiation to task termination

- The information in SWA is created when a job is interpreted and used during job initiation and execution

- It is pageable and swappable


78MVS

Anything that needs to be stored and accessed on user

request is a Data for MVS

Types of Data Business Data

– Database– Indexed Files– Flat Files

Application Components– Source Programs– Executable Programs– Screen Definitions– Record Layout Definitions– Command File Scripts

Data Management Overview

79MVS

Types of Data (Contd ..)

MVS (System) Data– O/S program– User Information (ID, Password, Profile)– Access Permissions

Temporary Data– O/S Built Data (e.g. task queues, segment table, page table)– Spooled Output– Work Files for Sort


80MVS

Dataset organization fall into two categories under MVS : VSAM and NON-VSAM

Non-VSAM provides four basic ways of organizing data stored in datasets- Physical Sequential- Indexed Sequential- Direct- Partitioned

VSAM provides four basic ways of organizing data stored in datasets- Entry Sequence Dataset - ESDS- Key Sequence Dataset - KSDS- Relative Record Dataset - RRDS- Linear Dataset - LDS

Dataset Organization

81MVS

Non-VSAM datasets organization

Physical Sequential Records are stored one after another in consecutive sequence Can reside on just any type of I/O devices Appropriate when file’s records don’t have to be retrieved at

random

Indexed Sequential Includes an index, which relates key field values to the

location of their corresponding data records


82MVS

Non-VSAM datasets organization

Direct Permits random access of records It doesn’t use an index To access record, the disk location address (By hashing) of

that record to be specified

Partitioned Consists of one or more members Each of these members can be processed, as if it were a

separate physical sequential file. Names of members in a Partitioned dataset(PDS) is stored

in a directory


83MVS

Partitioned Data Set - Salient Features– Commonly referred as PDS– Also known as Library– Used to store application components– PDS is divided into one or many members– Member name can be up to 8 characters long– There is no extension for member– Each member can be processed as an individual unit– Entire PDS can be processed as one unit– Each PDS contains a directory


84MVS

Partitioned Data Set - Salient Features (Contd ..)– Directory has an entry for each member in a PDS

• PDS Examples

PAYROLL.TEST.SOURCE, PAYROLL.PROD.SOURCE,

INV.TEST.LOADLIB

• Normally consists of 3 qualifiers called as– PROJECT– GROUP– TYPE


85MVS

Partitioned Data Set - Salient Features (Contd..)– Personal PDS start with high level qualifier as User

ID– E.g. DA00T23.NEW.SOURCE

– Member Name Examples– PAB0017, PAB0105, PAC0021 etc.

– Usually, the application component type cannot be identified from the member name. For that naming conventions are used for PDS.


86MVS

VSAM datasets organization

ESDSCan only reside on DASDFunctionally equivalent to Physical Sequential File

KSDS

Functionally equivalent to Indexed Sequential File

RRDS

Lets you retrieve the record by specifying the location relative to the start of the file

All VSAM datasets must be cataloged


87MVS

Data Organization - Salient Points– Non-VSAM Data Organization was developed in mid

1960s– VSAM - (Virtual Storage Access Method) was introduced

in early 1970s – VSAM was expected to replace Non-VSAM Data

Organization Functions– Today, most sites use both VSAM and Non-VSAM Data

Organization– VSAM is the primary data organization for user data– VSAM is also called as “native” file management system

of IBM– Most of the DBMS running under MVS use VSAM as

underlying Data Organization (e.g. DB2, IDMS)


88MVS

Data Organization - Salient Points (Contd ..) Physical Sequential Data Organization is used for

“flat” files Index Sequential and Direct Data Organization are

not very popular now (these functions are handled better by VSAM)

Partitioned Data Sets (PDS) also used by MVS to store O/S programs


89MVS

Data Set Naming Rules– Allows - Alpha, Digits, National Characters @,#$, and “.”– Maximum Length 44 characters for DASD, 17 for Tape – If Length is more than 8, must be broken into qualifiers of

maximum 8 characters each– Qualifiers are separated by “.”– “.” are counted in overall length– First character of the qualifier must be alpha or national

character– Last character of data set must not be “.”– First qualifier is called as high-level qualifier– High-level qualifier has special significance

Data Set Naming Rules

90MVS

E.g. Data Set name PAYROLL.P9710.TRAN Has three qualifiers High-level qualifier is PAYROLL Total length is 18

Data Set Naming Rules

91MVS

Data Set Tracking Mechanisms Label Catalog

Label– Data Set Label

First record of each data set is a label record called as; File label or Data Set Control Block (DSCB) There are several formats for DSCB DSCB describes data set’s name, it’s DASD location and other

details

Data Set Tracking

92MVS

Label (Contd..)– DASD Label Each DASD is labeled; called Volume Label (VOL1 label) DASD label is stored on a disk at third record of track 0 in

cylinder 0 DASD label contains Volume Serial Number and address

of the VTOC file

– Volume Serial Number Each DASD is identified by a unique number, Volume

Serial Number vol-ser Vol Ser must be specified for accessing the Data Set

(which is not cataloged)

Data Set Tracking

93MVS

Label (Contd..)– VTOC

• VTOC - Volume Table Of Contents is a special file for each DASD

• VTOC contains the file labels for all data sets on the volume

Data Set Tracking

94MVS

Label Processing When a dataset is stored on disk or tape, MVS identifies it with

special records called ‘labels’. There are 2 types of DASD labels : Volume, File Label All DASD volumes must contain a volume label, often called a

VOL1 label. This label is always in the same place on a disk volume : the 3rd record of track zero in cylinder zero.

Volume label has 2 important functions :

- It identifies the volume by providing a volume serial no. : Vol-ser. Every DASD volume must have a unique six-characters vol-ser.

- It contains the disk address of the VTOC.

MVS Datasets

95MVS

Label Processing (Contd..)

The VTOC (Volume Table of Contents) is a special file that contains the file labels for the datasets on the volume.

These labels are called Data Set Control Block (DSCB) have several formats called Format-1, Format-2 and so on.

MVS Datasets

96MVS

Vtoc

VOL 1 Label

Format-4VTOC

Format-1FileA

Format-IFile-B

Format-IFile-C

Format-3File-B

Format-5Free Extents

Free Extents

File-A

File-B

File-C

Free Extent

File-B

Free Extent

MVS Datasets

97MVS

Format-4-dscb : describes VTOC itselfFormat-1-dscb : *describes a dataset by supplying dataset name, DASD location & other characteristics[space is not allocated to DASD file in area called extents. Each extent consists of one or more adjacent tracks]

: * has room to define 3 extents for a file (1 primary, 2 secondary)

Format-3-dscb : *if file requires more than 3 extents, this dscb is created

*It contains room for 13 additional secondary extents[As a result file can contain upto 16 extents]Format-5-dscb : *contain information about free extents that aren’t allocated to files

* each can define upto 26 free extents

MVS Datasets

98MVS

Catalog• Obviates the need of specifying Vol Ser for the data set

Catalog Types• Master Catalog• User Catalog

Catalog Features• Each MVS has only one Master Catalog• Master Catalog is used by MVS for system data sets• User Catalog is used for user data sets• There can be multiple User Catalogs• Master Catalog contains one entry of each User Catalog

Catalog

99MVS

Catalog Features (Contd..)– VSAM data sets must be Cataloged– Non-VSAM Data Sets may or may not be cataloged– An Alias can be created for a Catalog

Usually, the high-level qualifier of a data set is same as the catalog name or catalog alias name

Multiple data sets can be cataloged in single user catalog Alias helps to catalog data sets with different high-level

qualifiers to be cataloged in a single user catalog

Catalog Name VCAT.MPS800 Alias MMA2 MMA1

Data Set Name MMA2.CUSTOMER.MASTER MMA1.CUSTOMER.TRAN

Catalog

100MVS

Data Management Functions (for Non-PDS) • Allocate• Process

– Add Records– Modify Records– Delete Records

• Deallocate (delete)• Copy• Rename• Catalog

Data Management

101MVS

Additional Functions for PDS• Compress• Member Management• Create, Modify, Delete, Copy, Rename

How Data Management is Achieved• Interactively using MVS Commands• Executing MVS Utility Programs (batch mode)• Through Application Programs

– On-line Processing– Batch Processing

Data Management

102MVS

How datasets are Accessed

Generally dataset goes through three phases when handled through program :

– Allocation– Processing– Deallocation

Allocation The process of locating an existing dataset or space for a new

dataset and preparing the system control block needed to use the dataset is called “Allocation”

Allocation occurs at 3 levels–Unit is selected and allocated e.g. SYSALLDA-DASD, TAPE –Volume is allocated–Dataset on that volume is allocated

MVS Concepts

103MVS

How datasets are Accessed (Contd ..) Processing

- Processing involves 3 steps• Opening datasets• Processing I/O• Closing datasets

Deallocation- Each file is automatically deallocated when job is finished with it- While deallocating, disposition of dataset can be decided, whether you want to retain the file or should be deleted

MVS Concepts

104MVS

What is a Job?– Simply put, job is execution of one or more related

programs in sequenceE.g. 1A job of creating an executable module (load module) from a

source program consists of executing Compiler program and executing Linker program.

E.g. 2A job of printing invoices may consist of execution of three

programs;– an EXTRACT program to pull out transactions from

database,– a SORT program for sorting the transactions,– a PRINT program to print the invoices.

Job Management Overview

105MVS

Job - Salient Points– Executed in a background mode– Job details are specified using some command language

Job Management Functions– Receive the job into operating system– Schedule the job for processing by O/S– Execute the Job– Process the output


106MVS

Stages of Job

1. Job Preparation• User keys-in commands using Editor• Save as a member in PDS

2. Job Scheduling• Initiated using TSO SUBMIT command • Not necessarily on FIFO basis• Prioritization is implemented using concept of class

and priority code

3. Job Execution


107MVS

Stages of Job (Contd..)

4. End of execution (normal, erroneous) Intimate the user Job log management Job output management

Printer output Data set output


108MVS

Erroneous Termination of job– Type of execution errors

• Incorrect commands (command syntax errors)• Required resources (Data Sets, Program Library,

Program Load Module) not available• Violation of access permissions for data sets, program

load module etc.• Mismatch in data set status; as required by job and as it

actually exists e.g. a create is issued for a data set while data set which already exists


109MVS

Erroneous Termination of job (Contd ..)• Program errors • Mismatch for Data set - Between program definition• and actual characteristics• Infinite loop• Data Type mismatch - numeric variable contains non-

numeric data– Any abnormal termination of program is called as “Abend”


110MVS

Definitions JOB :- Is the execution of one or more related programs in

sequence

JOB STEP :- Each program to be executed by a Job is called a job step

JCL (Job Control Language) :- Is a set of control statements that provide the specifications necessary to process a job

Job Management

111MVS

Definitions (Contd ..) JES (Job Entry Subsystem) :

- Ment for job entry into system, also for job returning after completion- Shares the load on the operating system- Takes care of all inputs and outputs- Do simple basic syntax checking- Resource Initialization- Creation of address space- It is also known as Job Scheduler- Classified into

JES2-design for uniprocessor environment JES3-design for multiprocessing environment (Decided at the time of system initialization)

- Jobs are sent to MVS depending on the class priority schemes

Job Management

112MVS

When you submit the job, JES reads the job stream(sequence of JCL commands) from a DASD file and copy it to a job queue, which is a part of a special DASD file called JES SPOOL.

How Job Is Entered Into the System

113MVS

How Job Is Scheduled For Execution MVS does not necessarily process jobs in the order in which

they are submitted. Instead, JES examines the jobs in the job queue and selects the most important jobs for execution. That way JES can prioritize its work, giving preference to more important jobs.

JES uses 2 characteristics to classify a job’s importance, both of which can be specified in the job’s JCL : Job Class and Job Priority

If two or more jobs are waiting to execute, the JES scheduler selects the one with higher priority

Job Scheduling

114MVS

Each job class is represented by a single character, either a letter (A-Z) or a digit (0-9). Job classes are assigned based on the processing characteristics of the job.

INITIATOR :- An initiator is a program that runs in the system region of an address space. Each initiator can handle one job at a time. It examines the JES spool, selects an appropriate job for execution, executes the job in its address space and returns to the JES spool for another job.

The number of active initiator on a system and as a result the number of address spaces eligible for batch job processing determines the number of batch jobs that can be multiprogrammed at once.

Job Scheduling

115MVS

Each initiator has one or more job classes associated with it. It executes jobs only from those classes.

Initiator Eligible Job Classes1 A2 B,C,D,H,L,T3 B,C,D,H,L,T

4 B,C5 B,C

6 C

Job Scheduling

116MVS

Within a job class, initiator selects jobs for execution based on their priorities, which can range from 0 to 15

If two or more jobs have same class & priority, they are executed in the order in which they are submitted.

Job Scheduling

117MVS

Once an initiator has selected job for execution, it invokes a program called the interpreter

The interpreter's job is to examine the job information passed to it by JES and create a series of control blocks in the SWA, a part of the address space’s private area

Among other things, these control blocks describes all of the datasets the job needs

Now initiator goes through 3 phases for each step of job- Allocation (required resources are allocated)

- Processing (region is created & program is loaded and executed)

- Deallocation (resources are released)

This continues until there are no more job steps to process

How Job Is Executed

118MVS

This continues until there are no more job steps to process Then, the initiator releases the job and searches the spool

again for another job from the proper class to execute As a user’s program to execute, it can retrieve data that was

included as part of job stream and stores in the JES spool

JES INITIATOR

Job

JCL SYSIN

SYSOUT QUEUE O/P DATA INTERPRETORPROGRAMEXECUTIONSYSOUT

How Job Is Executed

spool

119MVS

Like Jobs, SYSOUT data is assigned an output class that determines how the output will be handled

Common O/P classes are

A :- Printer

B :- Card Puch O/P

X :- Held O/P

[Held O/P stays on the sysout queue indefinitely; Usually, O/P is held so that it can be examined from a TSO terminal]

How The Job’s Output Is Processed

120MVS

After the job’s output has been processed, the job is purged from the system, i.e. JES spool space, the job used, is freed so it can be used by other jobs and any JES control blocks associated with the job are deleted

Once a job has been purged, JES no longer knows of its existence

How A Job Is Purged

121MVS

Dataset Allocation And Job Step Execution

SWAcontrol block

System RegionAllocation

Initiator

SWAcontrol block

System Region

Initiator

User Program

SWAcontrol block

System RegionInterpreter

Initiator

After initiator selects a job for execution, it invokes the interpreter, which builds therequired control blocks in the address space’s SWA.

For each job step, the initiator invokes allocation routines to allocate the units, volumes and datasets required by the job step

After resource allocation, the initiator creates a user region, loads the user program into itand transfers control to user program

122MVS

When the user program completes, the initiator invokes Unallocation routine to Deallocate the resources used by the job step

SWA CONTROL BLOCK

INITIATER

SYSTEM REGIONUNALLOCATION

Dataset Allocation And Job Step Execution

123MVS

Tools - A set of sub-systems and facilities that; Implement MVS functions Are directly used by MVS user

These are essentially Software programs; system programs

Tools Overview

124MVS

Interactive Processing Tools– TSO - Time Sharing Option

• Used by the terminal user to invoke MVS facilities interactively

• TSO internally treats each terminal user as a Job• Job Stream is created when terminal user logs in• Each terminal user is given a separate address

space

Tools Overview

125MVS

ISPF - Interactive System Productive Facility– Runs as part of TSO– Takes advantage of full screen (24 x 80) capability of 3270

terminals– Panels are provided for terminal users for issuing commands– Key Functions Implemented Using ISPF

• Editor - Program Sources, Job Commands• Data Management - PDS and Physical Sequential Data

Set Management• Job Processing - Initiate Job, Check job log• Miscellaneous

– PDF - Program Development Facility is Part of ISPF

Tools Overview

126MVS

Job Management Tools

Job Control Language (JCL) Used to code job commands Job Entry System (JES) Manages the job before and after execution; receive, schedule,

process output Base Control Program (BCP)

• Manages the job during execution Simultaneous Peripheral Operations on-line (SPOOL)

• Used for staging of input and output

127MVS

Why and What of JCL? JCL is the most dreaded word for newcomer to IBM world Why JCL?

– Since the job is executed in background, without user interaction, all information required for the execution must be supplied in advance

– JCL is used to specify this information


128MVS

Why JCL?– The most common information supplied through JCL is;

To whom the job belongs (which user id)? What is the program / utility that is to be executed? Where (in which library / PDS) to find the load module of

the program or utility? Where (which DASD volume / catalog, what data set

name) to find the input data files for the program / utility? Where should (which DASD volume, what data set name)

the output files be created? The printer output should be directed to which printer?


129MVS

What is JCL?– Stands for Job Control Language– Connotation is; set for job commands stored as a

MEMBER in a PDS – e.g. JCL to execute a batch program, JCL to compile

and link a COBOL program, JCL to allocate a VSAM data set, JCL to SORT and MERGE two Physical Sequential Data Sets

– Thus, JCL is nothing but a set of commands User keys-in commands using a editor Saves as PDS Member e.g.

PAYROLL.TEST.JCL(PROG1JCL)


130MVS

What makes learning JCL so difficult– JCL is powerful and flexible, that leads to some

complexity– It is non-intuitive– The user interface is formidable– The terms are ancient– Very little has changed since 1965 when JCL was first

developed

However, JCL can be understood and mastered with logical approach and open mind

Good grasp of JCL is a must to be a versatile IBM programmer


131MVS

Introduction

– Two versions of JES; JES2/JES3 JES2 is primarily for single processor systems

JES3 is for multiple processor systems

– Each MVS system uses either JES2 or JES3

– JES3 has additional scheduler functions than JES2 (e.g.

schedule job at specific time of the day, interdependent

job scheduling)

Jes - Job Entry System

132MVS

How Job Enters the System?– .Job can enter the system from local or remote card readers

(now obsolete)

– .By starting a cataloged JCL procedure (e.g. when user logs in, a predefined set of commands are executed as a batch job. These commands are stored as cataloged JCL procedure)

– .By interactive users ‘thru’ SUBMIT command. Users can create a PDS member in which commands are specified. On issuing SUBMIT command these are executed as a job

We will focus on third approach

MVS Tools Overview

133MVS

Input– On SUBMIT, internal reader reads the JCL and creates an

input stream– JES2 reads the input stream, assigns a Job Number and

places input stream in SPOOL data set (a message is sent to TSO user about the job number)

– Job is put in the conversion queue

Conversion– Converter program analyzes JCL statements– Converts into converter / interpreter text– Checks for Syntax errors

If any error, Job is queued for output processing If no error, Job is queued for processing

MVS Tools Overview

134MVS

Processing Selection based on job class and priority

– Selected job is passed to Initiator– Initiator invokes Interpreter– Interpreter builds control blocks from converter / interpreter

text in a Scheduler Work Area (SWA) SWA is part of address space’s private area Control blacks describe the data sets required by the job

MVS Tools Overview

135MVS

– Initiator allocates resources required by the Job Initiator starts the program to be executed Builds the user region Loads the program in the user region Transfers control to the program

– On completion of the program execution, initiator de-allocates the resources

– The process of allocation / execution and de-allocation is repeated for each job step

MVS Tools Overview

136MVS

Initiator Characteristics Each initiator can handle one job at a time

There can be multiple initiators

Each initiator has a job class associated with it

System Operators can control the number of initiators and the class/es

associated with each initiator

MVS Tools Overview

137MVS

Input Data Input data to the user’s program can be specified in the job

Called as in-stream data or SYSIN data

SYSIN data is read and stored in JES spool

SYSIN data is treated like a data coming from card reader

MVS Tools Overview

138MVS

Output

– Management of System Messages, User Data Sets that

need to be Printed / Punched

– Organized by output class and device set-up requirements

– User ‘s program can produce output data that is stored in a

JES spool; called as SYSOUT data

– Each SYSOUT data is assigned an output class

– Output class indicates the printer selection

MVS Tools Overview

139MVS

Output (Contd ..)

– “Held” Output Special class (usually Z) is assigned to “hold” the output “Held” output remains in the SYSOUT indefinitely Usually used to verify before printing User can change the class and thus release the “held” output

MVS Tools Overview

140MVS

Hard-copy Local or remote processing Device Selection Queue the output for print /punch

Purge Release SPOOL and Job Queue space Intimate TSO user about job completion

MVS Tools Overview

141MVS

Job Output– Output is produced at each stage job processing– Includes output produced by;

JES MVS User’s program where SYSOUT is allocated as output device

– Job output is available to user (you can see it dynamically)– It can be viewed using ISPF

MVS Tools Overview

142MVS

Components of Job Output– Component 1- Separator Page

First and last page of job output Inserted by JES Helps operator the segregate the job outputs when directed to printer

– Component 2 – part I Job Log Messages produced by JES Also displayed on operator’s console If the job Abends, error messages are logged in Job Log

MVS Tools Overview

143MVS

Component 2 – part II Job Statistics Summary information of system resources used by the job e.g.; Number of JCL cards Spool usage Execution time

Component 3 - JCL Listing– List of JCL that was processed for the job– Should be same as what user has created

MVS Tools Overview

144MVS

• Component 4 - Message Log– Messages regarding job execution– Messages produced by MVS– Includes details of– Resource Allocation– Program Execution– Resource De-allocation– Consists of Message label and message text– Message label starting with IEF indicates a MVS message– Installation specific messages

• Component 5 - SYSOUT– Separate sub-component for each SYSOUT allocation– Each SYSOUT can have different characteristics e.g.

class, record length etc.

MVS Tools Overview

145MVS

VTAM – Virtual Telecommunications Access Method– Telecommunications (TC) Access Method– Required to support terminal devices– Part of SNA – System Network Architecture– Provides centralized control over all terminals attached to

the system– VTAM Application programs (e.g. TSO, CICS IMS-DC)

communicate with terminal devices via VTAM

MVS Tools Overview

146MVS

CICS – Customer Information Control Program (optional component)– Interactive applications are developed using CICS– CICS is a VTAM application program– Works with VTAM to support on-line functions– CICS implements multi-programming within itself– Multiple programs which are part of same application are

executed within CICS address space– CICS selects one program at a time for execution

– CICS itself is multi-programmed by MVS along with other programs

MVS Tools Overview

147MVS

DB2 - DataBase 2 (optional component)– Database Management System– Relational Implementation

RACF - Resource Access Control Facility

– Comprehensive Security Package – Though optional used by most of the installations– Users and Resources (e.g. Data Sets) are identified to

RACF– Whenever user tries to access a resource the security is

checked by RACF– RACF is a set of routines– Invoked as and when required

MVS Tools Overview

148MVS

SMF - System Management Facility

Keeps track of system usage– CPU, DASD I/O, Records Printed etc.

Data collected when job is executed Stored in a special data sets Used for billing

MVS Tools Overview

149MVS

Language Translators / Linkage Editor / Loader– Language Translators- Convert source to object module– Separate for each language, Assembler Language Translator

is part of MVS– Linkage Editor (part of MVS) - Converts object module to

executable I.e. load module– Loader - Creates temporary load module (used during testing

phase)

MVS Tools Overview

150MVS

Utilities

– Set of general purpose programs

– Executed like a user program through JCL– Common Utilities are :

IEBGENER IEFBR14 SORT IDCAMS

MVS Tools Overview

151MVS

1. Create 2 PDSs with high level qualifier as your own MF login-id

2. Create 1 flat file EMPLOYEE with employee details like emp-no,emp-name, dept, desig, salary

3. See your created PDSs and file in hte dataset list

4. See, Browse, Edit the members of a PDS.

5. Copy 3 members from one PDS to another

6. Move one of the members from one PDS to another

7. Rename the moved member

8. Rename the members at the time of copying and moving

9. Write a sample COBOL program to display the hard coded values.

10. Make the proper alignment for the same program

11. Transfer the given member JCL to other user.

12. Delete the least important member from your PDS. Delete the memberless PDS.

Assignments on ISPF & TSO

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