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