Mainframe%20Overview

1
Mainframe Overview

• - If all the mainframes disappear, it would be
  the end of Western Civilization
  Martin Hopkins
• - What on earth is a mainframe David Stephens
• Available online at google books
• - On Website
• Mainframe Evolution paper from Research
• Mainframe Concepts Textbook

2
Why a mainframe?

• - Data Integrity
• - Throughput and Capacity
• - Response Time ..Especially under heavy loads
• - Disaster recovery
• - Usability??
• - Reliability Availability
• - Audit and recording
• - Security

3
Why not a mainframe?

• - Money
• Hardware Costs
• Software licensing
• People costs
• - People
• More people
• More training/person
• People Shortagegt higher salaries/person

4
Problems to leave the mainframe Is it there
only for historical reasons?

• - Buy the new hardware
• - Buy new software
• - REWRITE existing applications
• dusty deck syndrome
• - Gain experience with new environment
• Operations and User training
• - Establish new processes and procedures
• - Function testing on duplicate workloads
• - Stress testing
• The devil you know

5
Other Mainframe Considerations

• - Cloud computing
• As a provider of virtual hardware,
  platforms (HW OS subsystems), and
  applications
• e.g. email, disaster recovery
• - Local environment
• Overload conditions
• Workload variations e.g.Time of day,
  April 15
• Disaster situations..ability to adjust
• Expansion ..physical or logical
  (people)
• - Mobile Computers are increasing use of
  Mainframes

6
Mainframe Workloads

• - Batch
• Time Scheduled ..e.g Overnight
• Usually low priority during workday done
  in background
• -Transaction processing
• Usually dumb terminal to mainframe...
  PC simulates terminal
• Usually 3270 data-stream but can enhance
  if server and PC agree
• Servers in a client-server environment
  e.g. The Web
• 2 tier or 3 tier designs
• Where does application reside
  for 2 tier
• - On PC.. quicker response
  but maintenance headache
• - On Server ..
  maintainable, more secure
• - Software development (System and Application
  programs)

7
Workloads that may not be the best for a
Mainframe

• - Number Crunching
• - Graphics
• - Interactive
• games
• User interaction e.g. mouse,
  keystroke
• Give to Caesar the things the things
  that are Caesars

8
A little of mainframe history

• -1950s and 1960s
• many mainframe architectures , GE, RCA,
  DEC, UNIVAC all
• fail various reasons
• Amdahl and Fujitsu uniprocessor versus
  SMP architecture
• -Technology jump i.e from Bipolar to
  CMOS
• from amps to FETs
• heat the big issue
• Number Crunching parallel
  computation

9
Communications TCP/IP Diagram
10
A little bit of architecture

• -See fig 1 and 2
• Explain Processor, multiprocessor Channels,
  Control Units (CUs)
• Multiple CUs per channel
• Multiple Channels to each CU
• Multiple CU for each device e.g. 2 tailed
  switch
• PR/SM
• Coupling Facility
• -Now on to the z Architecture

11
Workload Summary

• - Number Crunching
• - Batch
• - Servers for Networks
• Transaction processing
• The Web
• - Software development (System and
  Application programs)