Brief Intro to Mainframe and z/OS Administration

By Luis F. Bustamante

What is a mainframe?

What is a mainframe?

What is a mainframe?

• Developed in 1950s

• First mass-produced digital, all-transistorized, business computer that could be afforded by many businesses worldwide.

• 1st general purpose computers

• Designed with business applications in mind

What is a mainframe?

• Market dominated by IBM (90%+) – Made in Poughkeepsie, NY

• Large-Scale computing

• Large Enterprises

• z Architecture (not x86 or x64)

• Run various Operating Systems – z/OS

– z/VM

– Linux

What is a mainframe?

• Runs Multiple OS instances - LPAR

• Serves tens of thousands of users

• Manages petabytes of data

• Very reliable

• Used for Mission Critical Applications

• Expensive (Cost Savings from Consolidation)

• Scalable (After initial investment)

• Highly secure

• Large Data processing

• Central data repository

What is a mainframe?

Typical Mainframe Workloads

Batch Workload •Reports •Data consolidation •Billing •Account statements •Data Analytics

Transactions

• Quick interactions - Seconds, or fractions of seconds

• Millions/billions transactions per day

• Thousand of concurrent users

• Require high availability

• Examples: – Banks: ATM, Tellers, Financial Records

– Airline reservations

– Inventory control

– Government: Tax processing, license issuance and management

Transactions

• Usually under CICS in z/OS:

• CICS – Transaction Server

– HTTP (REST, SOAP)

– Web

– Java

– Cobol

– C/C++

Roles in the Mainframe World

Who uses mainframes?

• 80% of fortune 500 companies

• Banking

• Finance

• Health care

• Insurance

• Public utilities

• Government

What is z/OS?

• Most common mainframe OS • EBCDIC (Extended Binary Coded Decimal Interchange Code)

character set as opposed to ASCII • Implements POSIX compliant UNIX kernel to run UNIX type

applications. • All kinds of workloads:

– COBOL: usually legacy applications – Web services/interfaces. – C/C++, Java, PL/I

• Highly Secure – RACF security server • Networking:

– TCP/IP - Under Unix System Services – VTAM - legacy communications/networking protocol. Still widely

used.

• Not Suitable for Complex computational workloads

Parallel Sysplex

z/OS Clustering technology:

• Up to 32 tightly coupled z/OS images

• Add and remove dynamically

• Distributed applications workload

• Network Load Balancing and fail over.

• 99.999% availability

• Use of coupling facility – Shared communications channel

– Resource management and serialization

Common z/OS software setup • Security System: Usually RACF • Compilers • Relational Database: DB2 most common • Transaction processing facility:

– CICS – IMS – WebSphere Application Server for z/OS

• Sort Program • SDSF – System Display and Search Facility • Job Scheduling Software – Batch Management • WebSphere MQ for asynchronous application

messaging • Other utilities.

Networking on z/OS

• IBM Communications Server for z/OS – VTAM /SNA Systems Network Architecture 1969

• IBM proprietary

• Being phased out

• Hierarchical Network Model. Mainframe Centric

• 1 Mainframe owns terminal and other network devices

• Not compatible with TCP/IP

SNA has evolved, many applications still use it. Enterprise Externder (SNA over IP) allows it to operate over TCP/IP netwoks

Networking on z/OS - SNA

Networking on z/OS

• IBM Communications Server for z/OS

– TCP/IP and Networking Related Products

• TN3270

• SMTP

• BIND

• FTP

– VIPA and DVIPA

– Sysplex Distributor (load balancing)

– OSPF

Networking on z/OS – TCP/IP in a sysplex

Interacting with z/OS

• TN3270 emulator

– TSO/E

– ISPF

– z/OS Console

• SSH – UNIX System Services

Interacting with z/OS

• TN3270 emulator

– IBM’s terminal emulation software

– Runs over telnet (Port 23)

– Can be (it usually is) encrypted using SSL

• TSO/E

– Command line interface

– Replaced by ISPF although TSO commands are still used for systems management and REXX scrips

Interacting with z/OS • TSO/E

Interacting with z/OS

• ISPF

– Panel driven

– Access to multiple utilities and programs for dataset manipulation

– ISPF Editor – for editing and viewing datasets

Interacting with z/OS • ISPF

Interacting with z/OS

• z/OS console – Used to interact directly with the operating

system • Startup

• Shutdown

• Task management – There are better ways

• Reply to system and application messages

– Displays ALL operating system messages and other system related software.

– Used mostly by operations personnel

Interacting with z/OS

• JCL – Job Control Language

– In z/OS everything runs as a Job, including users

– Used to be entered using punch cards

– Used for batch processing

– Specifies runtime options

– Specifies input and output datasets

Interacting with z/OS • JCL – Job Control Language:

Interacting with z/OS

• SDSF

– Job/process management

– Operating System log

– Job Output Display

– Allows for console command entry

Interacting with z/OS

• SDSF

z/OS and UNIX comparison

z/OS and UNIX comparison

z/OS and UNIX comparison

z/OS and UNIX comparison

• NO root user – User access is managed according to roles, even under Unix System Services

• NO hierarchical file system - z/OS uses catalogs to store dataset information

– Master Catalog: Think of it as the root of the file system. It points to multiple user catalogs.

UNIX within z/OS

• A.K.A UNIX System Services or z/OS UNIX

• POSIX and XPG4 compliant

• Java

• TCP/IP

• Other ported utilities

• Accessed via: – OMVS: Shell like interface

– ISPF Shell: Panel Driven Interface

– SSH: tcsh shell interface

DEMO

YAY!!!!

Additional reading

Introduction to the New Mainframe series:

http//:redbooks.ibm.com

Additional reading

IBM’s Master the Mainframe Contest:

http://www.ibm.com/developerworks/university/students/contests/mainframe/details.html

IBM’s z/OS Basics infocenter:

http://publib.boulder.ibm.com/infocenter/zos/basics/index.jsp

IBM’s Academic Initiative Website:

http://www-03.ibm.com/ibm/university/academic/pub/page/systemz