Basics of Mainframe Computing Boot Camp · PDF file• IBM designers coined the word Data...

SECURITY & COMPLIANCE CONFERENCE 2016

Basics of Mainframe

Computing – Boot Camp

John Hilman

Vanguard Professional Services

VANGUARD SECURITY & COMPLIANCE 2016

Legal Notice

Copyright

©2016 Vanguard Integrity Professionals, Inc. All Rights Reserved. You have a limited license

to view these materials for your organization’s internal purposes. Any unauthorized

reproduction, distribution, exhibition or use of these copyrighted materials is expressly

prohibited.

Trademarks

The following are trademarks of Vanguard Integrity Professionals – Nevada:

©2016 Vanguard Integrity Professionals, Inc. 2

Vanguard Administrator

Vanguard Advisor

Vanguard Analyzer

Vanguard SecurityCenter

Vanguard Offline

Vanguard Cleanup

Vanguard PasswordReset

Vanguard Authenticator

Vanguard inCompliance

Vanguard IAM

Vanguard GRC

Vanguard QuickGen

Vanguard Active Alerts

Vanguard Configuration Manager

Vanguard Configuration Manager Enterprise Edition

Vanguard Policy Manager

Vanguard Enforcer

Vanguard ez/Token

Vanguard Tokenless Authenticator

Vanguard ez/PIV Card Authenticator

Vanguard ez/Integrator

Vanguard ez/SignOn

Vanguard ez/Password Synchronization

Vanguard Security Solutions

Vanguard Security & Compliance

Vanguard zSecurity University


The following are trademarks or registered trademarks of the International Business Machines Corporation: Java and all Java-based trademarks are trademarks of Oracle and/or its affiliates. UNIX is a registered trademark of The Open Group in the United States and other countries.

Microsoft, Windows and Windows NT are registered trademarks of Microsoft Corporation.

Other company, product, and service names may be trademarks or service marks of others.

Trademarks


CICS

CICSPlex

DB2

eServer

IBM

IBM z

IBM z Systems

IBM z13

S/390

System z

System z9

System z10

System/390

VTAM

WebSphere

z Systems

z9

z10

z13

z/Architecture

z/OS

z/VM

zEnterprise

IMS

MQSeries

MVS

NetView

OS/390

Parallel Sysplex

RACF

RMF


Session Topics

• What Makes a Mainframe?

• Working in TSO

• Using ISPF

• What is an MVS™ Data Set?

• How to Create a File

• What is a Batch Job?

• Glossary of Terms



What Makes a Mainframe?


z/OS®

Hardware Software

TSO DB2®

JES

IMS™

Storage

Applications

UNIX®

DASD

VOL123

VOL987

CICS®


Early Operating Systems

Support for System/360

• OS/360 - 1964

– PCP (Primary Control Program)

– MFT (Multiprogramming – fixed number of tasks)

– MVT (Multiprogramming – variable number of tasks)



History of MVS


z/OS

2001

OS/390®

1996

MVS/ESA 1988

MVS/XA 1981

MVS/SP 1979

OS/VS2 MVS 1974 16 MB

16 MB

2 GB

2 GB

2 GB

16 EB


Mainframe Applications - TSO

• TSO – Time Sharing Option

– Allows multiple users to use the operating system at the

same time

– Powerful text editor

– Utilities to create / manage data sets / and submit batch

jobs

– Restructured Extended Executor (REXX) language

support

• REXX is a high-level procedures language that enables

inexperienced users as well as experienced programmers to write

structured programs called REXX execs.

– Ability to execute programs interactively



“Native” TSO


• Provides a limited command interface

to the operating system

• Ability to issue RACF® commands

directly from the READY prompt


Mainframe Applications - ISPF

• ISPF - Interactive System Productivity Facility

– Panel application navigated by entering options

– Provides full-screen text editor and browser

– Utilities for creating, locating, listing and deleting files

– Functions to manage data sets and submit jobs

– Utilize “fastpath” to functions

• Example - enter 3.4 for Data Set List Utility

– TSO command function within ISPF

• Option 6 – ISPF Command Shell



ISPF Primary Options Menu



Mainframe Applications - CICS & DB2

• CICS – Customer Information Control System

– Transaction processor

– Designed for rapid, high-volume online processing

– Enables the user (through the application) to access a

number of protected resources in a database (DB2) or file

system

– Isolates concurrent users from each other so that two

users cannot update the same resource at the same time

• DB2 – Data Base 2

– Relational database management system (RDMS)

– Reduces redundancy in data storage



Mainframe Applications - z/OS UNIX®

• z/OS UNIX System Services

– Best of both worlds: UNIX and z/OS

– UNIX Kernel integrated into the operating system

– Hierarchical file system (HFS) familiar to UNIX users

– Applications can work with data in both the z/OS UNIX file

systems and traditional z/OS data sets

• FTP – File Transfer Protocol

– Protocol of choice to transfer data over the Internet

– Most widely used TCP/IP applications on z/OS

– Supports both z/OS data sets and files in the z/OS UNIX

file system



Connecting to the Mainframe


TCP/IP

SNA


‘Green Screen’ Terminals


• IBM® 3270 - “Display

Device”

• Known as ‘Green Screen’

• IBM 3270 protocol used

today in Terminal Emulation

software: Attachmate

Reflection, IBM PCOMM,

Host Explorer, Passport,

and others

http://upload.wikimedia.org/wikipedia/commons/a/a8/IBM-3279.jpg


Today’s “Green Screen”



Logging On



Password Screen



Line Mode TSO



Issuing TSO Commands



Using ISPF



ISPF Main Menu



z/OS Files

• To Make a File we: – group characters together to form a field

– group fields together to collect information to form a record

– place records together which results in a file

• IBM designers coined the word Data Set – – Collection of logically related data records

– Stored in DASD - Direct Access Storage Device


DASD

VOL123


A Single Record Contains Fields


Smith, Jane 026548791 Checking $ 3,824

Fields

bank account

number

customer

name type of bank

account balance

Record


Multiple Records Make up a Data Set


Arnold, Ben 036589294 Checking

Account $ 12,139

Black, Sally 029639211 Checking

Account $ 8,146

Mason, Bob 028538692 Checking

Account $ 9,632

Smith, Jane 026548791 Checking

Account $ 3,824

Data Set


Data Set Name Characteristics

• Length

– maximum 44 characters

• Made up of qualifiers

– 1 to 8 characters per qualifier

– qualifiers cannot start with a numeric or hyphen (–)

• First qualifier referred to as high-level qualifier (HLQ)

or high-level index (HLI)


VANGUARD PRODUCT MONTHLY REPORT FILE . . . .

qualifier separator


Types of Data Sets

• Sequential Data Set

– A file which is a collection of records written and read in

sequential order from start to finish

• Partitioned Data Set or Library

– A data set containing one or more members, similar to a

directory or folder in other types of file systems

• VSAM Data Set (Virtual Storage Access Method)

– A data set that is a collection of records, grouped into

control intervals, accessible by applications using the

VSAM access method



Viewing a Data Set – Option 1



The View Panel



Alternate Way to Enter Data Set Name



Display ISPF Profile



Profile Settings


Turn off PREFIX with PROFILE command:

TSO PROFILE NOPREFIX


Viewing the Data Set



Editing a Data Set – Option 2



The Edit Panel



Alternate Way to Enter Data Set


With PREFIX off, must specify full data set name


Editing the Data Set



Creating a New Data Set – Option 3



Data Set Utility



Allocating a New Data Set


If PREFIX is on, you must use quotes around data set name if the prefix is specified


Specify Allocation Information



Another Way to Allocate a Data Set



Copy All Members From a Data Set



Specify the Copy-To Data Set



Use the Same Allocation Attributes



Using Data Set List



Specify the HLQ (PREFIX)



Use the '/' to Select Action



List of Actions



Batch Jobs

• Batch - deferred processing

• Online - now and interactive

• z/OS has unique capacity to handle lots of jobs

concurrently

• Jobs are controlled by JES – Job Entry Subsystem



Getting Work Done in z/OS


JES receives jobs into the operating system, schedules them for

processing, and controls their output processing

z/OS

INPUT

OUTPUT

SYSOUT

RJE/RJP

NJE

Line & PSF Printers

JES

SYSIN

JOB

SUBMIT

BATCH

RJE/RJP

NJE

TSO


Executing Programs in Batch

• Executing a program means running it to accomplish

what you intend to do

• To run, a program must be:

– copied from disk into memory

– associated with the data sets it will use

– given control by z/OS

• To execute a program in batch, the job is submitted

– Job Control Language (JCL) tells JES how to execute the

program



A Sample Batch Job



SDSF Provides:

• Information to monitor, manage, and control the

output of jobs in the z/OS system

• Current information about jobs, output, devices and

system resources



SDSF Allows You To:

• Control job processing (hold, release, cancel jobs)

• Control output, and browse jobs without printing

• Control devices such as printers, lines, and initiators

• Browse the syslog

• Manage system resources, such as members of the

MAS (Multi-Access Spool), job classes, and WLM

(Work Load Manager) enclaves

• Monitor and control the IBM Health Checker for

z/OS checks



SDSF Main Menu



Working with JES Queues

SDSF Panel JES Queue

DA (displays the execution queue) Provides information about each job,

started task, and TSO user that is being

processed by the system

I (input queue) Provides information about each job,

started task, and TSO user that is on the

JES input queue

O (output queue) Provides information about the output

data sets from jobs, started tasks, and

TSO users

H (held output queue) Provides information about the output

from jobs that are on hold

ST (status queues) Provides information about the jobs that

are on any JES queue



Viewing Job Output



Glossary of Terms

A

access authority

One of a range of possible authority levels that control access to protected resources. In RACF, the access authorities are: NONE, EXECUTE,

READ, UPDATE, CONTROL, and ALTER.

access group

A type of member group used to define access control.

access list

The part of a resource profile that specifies the users and groups that may access the resource and the level of access granted to each.

ACEE - access control environment element

A control block containing details of the current user, including user ID, current connect group, user attributes, and group authorities. An ACEE is

constructed during user identification and verification.

address space

(1) The actual memory used by an active program.

(2) A range of up to two gigabytes of contiguous virtual storage addresses that the system creates for the user.

AUDITOR attribute

A user attribute that allows the user to specify logging options on the RACF commands and list any profile (including its auditing options) using the

RACF commands.

B

base segment

The portion of a RACF profile that contains basic information needed to define a user, group, or resource to RACF. Also called RACF segment.

batch job

A predefined group of processing actions submitted to the system to be performed with little or no interaction between the user and the system.

batch processing

A method of running a program or a series of programs in which one or more records (a batch) are processed with little or no action from the user

or operator.



Glossary of Terms

C

CICS (Customer Information Control System)

An IBM licensed program that provides online transaction-processing services and management for business applications.

class

A collection of defined entities (users, groups, and resources) with similar characteristics. The class names are USER, GROUP, DATASET,

and the classes that are defined in the class descriptor table.

class authority (CLAUTH)

An authority that allows a user to define RACF profiles in a class defined in the class descriptor table. A user can have class authority to one

or more classes.

class descriptor

An entry in the CDT. Each class descriptor associates a class name with one or more CICS resources. A class descriptor should exist for

every class except USER, GROUP, and DATASET.

CDT - class descriptor table

A table containing class descriptors. The CDT contains descriptors with default class names for CICS resources. Users can modify the

supplied descriptors and add new ones.

console

An input/output device on a computer, reserved for communication between the computer operator or maintenance engineer and the

computer.

current connect group

During a terminal session or batch job, the group with which a user is associated for access checking purposes. On MVS, if a user does not

specify the current connect group on the LOGON command or batch JOB statement, the current connect group is the user's default group.



Glossary of Terms

D

DASD volume

A direct access storage device (DASD) space identified by a common label and accessed by a set of related addresses.

DES - Data Encryption Standard

A cryptographic algorithm designed to encrypt and decrypt data using a private key

DFP - Data Facility Product

A program that isolates applications from storage devices, storage management and storage device hierarchy management.

DFSMS - Data Facility Storage Management Subsystem

An operating environment that helps automate and centralize the management of storage. To manage storage, DFSMS provides the storage

administrator with control over data class, storage class, management class, storage group, and automatic class selection routine definitions.

data set

The name that refers to files on an IBM mainframe computer, typically stored on DASD or magnetic tape.

data set profile

A profile that provides RACF protection for one or more data sets. The information in the profile can include the data set profile name, profile

owner, universal access authority, access list, and other data.

data space

A range of up to two gigabytes of contiguous virtual storage addresses that a program can directly manipulate. Unlike an address space, a data

space can hold only data; it does not contain common areas or system data or programs.

DB2

A family of IBM licensed programs for relational database management.

default group

In RACF, the group specified in a user profile that is the default current connect group.

discrete profile

A resource profile that provides RACF protection for a single resource.

DSMON – Data Security Monitor

A RACF auditing tool that produces reports enabling an installation to verify its basic system integrity and data security controls.



Glossary of Terms

E

ESA - Enterprise Systems Architecture

A hardware architecture that reduces the effort required for managing data sets and extends addressability for system, subsystem, and

application functions.

ESA/390 Enterprise Systems Architecture/390

An IBM architecture for mainframe computers and peripherals. Processor systems that follow the ESA/390 architecture include the ES/9000

family

erase-on-scratch

A Resource Access Control Facility (RACF) and DFSMSdfp function that overwrites the space occupied by a data set when the data set is

deleted (scratched) from a direct access storage device (DASD).

exabyte (EB)

For processor, real and virtual storage capacities and channel volume: 1,152,921,504,606,846,976 bytes, or 2 to the power of 60, or 1024 to

the power of 6.

extended addressing

The use of 31-bit addresses (above the 16MB line), which multiplies by 128 the range of virtual storage that can be addressed.

F

failsoft processing

Processing that occurs when no data sets in the primary RACF database are available (RACF is installed but inactive).

fully-qualified data set name

A data set in which all the qualifiers are completely spelled out.



Glossary of Terms

G

general resource

Any system resource, other than an MVS data set, that is defined in the class descriptor table (CDT). On MVS, general resources include DASD

volumes, tape volumes, load modules, terminals, IMS and CICS transactions and other CICS resources, and installation-defined resource classes.

general resource profile

A profile that provides protection for one or more general resources. The information in the profile can include the general resource profile name,

profile owner, universal access authority, access list, and other data.

generic profile

A resource profile that can provide RACF protection for zero or more resources. The resources protected by a generic profile have similar names

and identical security requirements.

gigabyte (GB, Gbyte)

For processor, real and virtual storage capacities and channel volume: 1,073,741,824 bytes, or 2 to the power of 30, or 1024 to the power of 3.

global access checking

A RACF feature that permits access to protected, frequently opened files much faster than otherwise possible. After the establishment of an in-

storage table of default values containing authorization levels for selected resources, access to those resources is granted without performing

security checks as long as the requested access authority does not exceed the global value. Global access checking can grant a user access to

the resource, but it cannot deny access

group data set

A RACF-protected data set in which either the high-level qualifier of the data set name or the qualifier supplied by an installation exit routine is a

RACF group name.

H

hiperspace

A high-performance, virtual-storage space of up to 2 gigabytes (GB). Unlike an address space, a Hiperspace contains only user data and does not

contain system control blocks or common areas; code does not execute in a Hiperspace. Unlike a data space, data in a Hiperspace cannot be

referenced directly; data must be moved to an address space in blocks of 4 KB before being processed. The 4-KB blocks can be backed up by

expanded storage or auxiliary storage, but never by virtual storage.

HLQ

High-level qualifier. The first qualifier of a data set name.



Glossary of Terms

I

IBM – International Business Machines

IMS - Information Management System

Any of several system environments available with a database manager and transaction processing, capable of managing complex

databases and terminal networks.

IPL - initial program load

(1) The process that loads the system programs from the system auxiliary storage, checks the system hardware, and prepares the system

for user operations.

(2) The initialization procedure that causes an operating system to begin operation.

(3) The process of loading system programs and preparing a system to run applications.

I/O - input/output

Pertaining to a device, process, channel, or communication path involved in data input, data output, or both.

ISPF - Interactive System Productivity Facility

An IBM licensed program that serves as a full-screen editor and dialog manager. Used for writing application programs, it provides a means

of generating standard screen panels and interactive dialogs between the application programmer and terminal user.



Glossary of Terms

J

JCL - job control language

A command language that is used to identify a job to an operating system and to describe the job's requirements.

JES - Job Entry Subsystem

An IBM licensed program that receives jobs into the system and processes all output data that is produced by jobs.

JES2

An MVS subsystem that receives jobs into the system, converts them to internal format, selects them for execution, processes their output,

and purges them from the system. In an installation with more than one processor, each JES2 processor independently controls its job

input, scheduling, and output processing.

JES3

An MVS subsystem that receives jobs into the system, converts them to internal format, selects them for execution, processes their output,

and purges them from the system. In complexes that have several loosely coupled processing units, the JES3 program manages

processors so that the global processor exercises centralized control over the local processors and distributes jobs to them via a common

job queue.

job

(1) A resource that consists of a task and its preconfigured parameters. Among other things, the parameters specify the targets on which the

job is to run.

(2) A separately executable unit of work defined by a user, and run by a computer.



Glossary of Terms

L

list-of-groups checking

A RACF option that allows a user to access all resources available to all groups of which the user is a member, regardless of the user's current

connect group. For any particular resource, RACF allows access based on the highest access authority among the groups of which the user is a

member.

load library

A library containing load modules.

load module

A program in a form suitable for loading into main storage for execution. A load module is the output of the linkage editor.

load module library

A partitioned data set (PDS) used to store and retrieve load modules.

logging

The recording of audit data about specific events.

M

MAC - mandatory access control

A means of restricting access to objects on the basis of the sensitivity (as represented by a label) of the information contained in the objects and

the formal authorization (clearance) of subjects to access information of such sensitivity.

mainframe

A computer, usually in a computer center, with extensive capabilities and resources to which other computers may be connected so that they can

share facilities.

main storage

Program-addressable storage from which instructions and other data can be loaded directly into registers for subsequent execution or processing.

multilevel security

A security policy that allows the classification of data and users based on a system of hierarchical security levels (for example: unclassified, secret,

top secret) combined with a system of non-hierarchical security categories

MVS - Multiple Virtual Storage

The mainframe operating system that allows multiple users to work simultaneously using the full amount of virtual storage.



Glossary of Terms

O

OPERATIONS attribute

A user attribute that grants the equivalent of ALTER access to all data sets unless the user or one of the user’s connect groups appears

explicitly in the access list of a data set’s profile.

operating system (OS)

A collection of system programs that control the overall operation of a computer system.

OS/390

Pertaining to the IBM operating system that includes and integrates functions previously provided by many IBM software products (including

the MVS operating system) and (a) is an open, secure operating system for the IBM S/390 family of enterprise servers, (b) complies with

industry standards, (c) is enabled for network computing and e-business, and (d) supports technology advances in networking server

capability, parallel processing, and object-oriented programming.

owner

The user or group that creates a profile, or is named the owner of a profile. The owner can modify, list, or delete the profile.

P

PDS - partitioned data set

In a z/OS environment, a data set in direct-access storage that is divided into partitions, which are called members. Each partition can

contain a program, part of a program, or data.

POSIT

A keyword in the ICHERCDE macro that determines the position of a resource class in the RACF class descriptor table (CDT). All classes

with the same POSIT value are controlled together by the SETROPTS command.

profile

Data that describes the significant characteristics of a user, a group of users, or one or more computer resources. A profile contains a base

segment, and optionally, a number of other segments.

protected user ID

A user ID that cannot enter the system by any means that requires a password, and cannot be revoked by invalid password attempts.



Glossary of Terms

R

RACF - Resource Access Control Facility

An IBM licensed program that provides access control by identifying users to the system; verifying users of the system; authorizing access

to protected resources; logging detected, unauthorized attempts to enter the system; and logging detected accesses to protected resources.

RACF database

The repository for the security information that RACF maintains.

RACF data set

One of the data sets comprising the RACF database.

RACF report writer

A RACF function that produces reports on system use and resource use from information found in the RACF SMF records.

RACF segment

The portion of a RACF profile that contains basic information needed to define a user, group, or resource to RACF. Also called base

segment.

RACINIT request

In RACF, the issuing of the RACINIT macro or the RACROUTE macro with REQUEST=VERIFY or REQUEST=VERIFYX specified. A

RACINIT request is used to verify the authority of a user to enter work into the system.

RACROUTE

In RACF, a macro that provides a means of calling RACF to provide security functions.



Glossary of Terms

resource authorization

The facility for checking a user's level of access to a resource against the user's desired access or the result of that check.

resource group class

A RACF class in which resource group profiles can be defined. A resource group class is related to another class, sometimes called a

member class. For example, resource group class GCICSTRN is related to class TCICSTRN.

resource group profile

A general resource profile in a resource group class. A resource group profile can provide RACF protection for one or more resources with

unlike names.

resource manager

An application, program, or transaction that manages and controls access to shared resources such as memory buffers and data sets.

WebSphere MQ, CICS, and IMS are resource managers.

resource profile

A profile that provides RACF protection for one or more resources. User, group, and connect profiles are not resource profiles. The

information in a resource profile can include the data set profile name, profile owner, universal access authority, access list, and other data.

Resource profiles can be discrete profiles or generic profiles.

RESTRICTED attribute

A user attribute that can be assigned to a shared user ID, such as PUBLIC or ANONYMOS, or a user ID used with a certificate name filter,

to prevent the user ID from being used to access protected resources it is not specifically authorized to access.

REVOKE attribute

A user attribute that prevents a RACF-defined user from entering the system.

RRSF – RACF Remote Sharing Facility

The RACF remote sharing facility allows RACF to communicate via APPC with other MVS systems that use RACF, allowing you to maintain

remote RACF databases and synchronize passwords across the systems.



Glossary of Terms

S

S/390

IBM enterprise servers based on Enterprise Systems Architecture/390 (ESA/390). The S/390 has been superseded by the IBM System z.

SAF - system authorization facility

An interface defined by MVS that enables programs to use system authorization services in order to control access to resources, such as data

sets and MVS commands.

security policy

A written document that defines the security controls that you institute for your computer systems. A security policy describes the risks that you

intend these controls to minimize and the actions that should be taken if someone breaches your security controls.

sequential data set

A data set whose records are organized on the basis of their successive physical positions, such as on magnetic tape.

SMF - System Management Facility

A z/OS facility that collects and records a variety of system and job-related information. Examples of information collected by SMF are statistics,

accounting information, and performance data.

SPECIAL attribute

A user attribute that gives the user full control over all of the RACF profiles in the RACF database and allows the user to issue all RACF

commands, except for commands and operands related to auditing.

Sysplex

A set of z/OS systems that communicate with each other through certain multisystem hardware components and software services.

System z

IBM enterprise servers based on z/Architecture.

T

TSO - Time Sharing Option

In a z/OS or OS/390 environment, software that provides interactive communications, allowing a user or programmer to start an application from a

terminal and work with the application.

task

A basic unit of work to be performed or a process and the procedures that run the process.



Glossary of Terms

U

UACC - universal access authority

The default access authority that applies to a resource if the user or group is not specifically permitted access to the resource. The universal

access authority can be any of the access authorities.

UADS - user attribute data set

In TSO, a partitioned data set with a member for each authorized user. Each member contains the appropriate passwords, user

identifications, account numbers, LOGON procedure names, and user characteristics that define the user.

USS - UNIX System Services

A component of z/OS or OS/390 that provides a UNIX environment.

user data set

A data set defined to RACF in which either the high-level qualifier of the data set name or the qualifier supplied by an installation exit routine

is a RACF user ID.

user identification and verification

The acts of identifying and verifying a RACF-defined user to the system during logon or batch job processing. RACF identifies the user by

the user ID and verifies the user by the password or operator identification card supplied during logon processing or the password supplied

on a batch JOB statement.



Glossary of Terms

V

volume

(1) A representation of an actual physical storage device or unit on which the objects in your system are stored.

(2) A storage medium that is put on or taken off the system as a unit, for example, magnetic tape or diskette.

(3) A unit of storage on disk, tape, or other data-recording media.

VIP - Vanguard Integrity Professionals

VTOC - volume table of contents

A table on a direct access volume that describes the location, size and other characteristics of each data set on the volume.

VSAM - Virtual Storage Access Method

An access method for direct or sequential processing of fixed-length and varying-length records on direct access devices. The records in a

VSAM data set or file can be organized in logical sequence by a key field (key sequence), in the physical sequence in which they are written

on the data set or file (entry-sequence), or by relative-record number.

Z

z/Architecture

An IBM architecture for mainframe computers and peripherals. The System z family of servers uses the z/Architecture. It is the successor to

the S/390 and 9672 family of servers.

z/OS

An operating system for the IBM eServer product line that uses 64-bit real storage.

z/OS UNIX System Services

The set of functions provided by the shell and utilities, kernel, debugger, file system, C/C++ Run-Time Library, Language Environment, and

other elements of z/OS that allows users to write and run application programs that conform to UNIX standards.


Basics of Mainframe Computing Boot Camp · PDF file• IBM designers coined the word Data...

Documents

Transcript of Basics of Mainframe Computing Boot Camp · PDF file• IBM designers coined the word Data...