Transcript Business Transactions

Transaction Processing Systems
Lecture Week 2
27 July 1998
Learning Objectives
• Identify Business Transactions and how
Management Support Systems use
transaction data
• Become familiar with Transaction
Processing System components and main
properties
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Transactions
• Keep record of exchange of goods and
services so we can have them for later
reference
• History
– 6000 years ago Sumerians invented writing and
a recording system to recording changes in
royal inventory; land, livestock, jewels, …
– Moved from clay tablets to paper and
eventually databases stored on the computer
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Transactions on Computer
• Early developments in storing transactions
on computer influenced by need for fast,
accurate recording for large payroll
processing
• Database is an abstraction of the current
state of the business, snap shot prior to any
changes
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Business Transactions
• Why do businesses have transactions
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Sell Products
Exchange Goods
Inform Customers
Deliver Service
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Business Transactions
• Why do businesses record transactions
– So they pay the right amount of tax to the IRD
– So people get what they are promised
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pay check
service
good
loan check
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Business Transactions
• A business transaction is defined as an
exchange between the organisation and
another organisation or individual.
• We use computer systems to record business
transactions because
– Scalability - as business grows so does system
– Reliability - computers don’t misplace files
– Cost
- would need army of people to
track transactions
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Examples of Business
Transactions
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Banking
Securities Trading
Insurance
Inventory Control
Manufacturing
Retail
Government
Internet
Telecommunications
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Deposit/Withdraw Money
Buy/Sell Shares
Pay premium
Record shipment arrival
Log work-in-process
Record sale
Register automobile
Purchase at Amazon.com
Connect and bill calls
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How is Transaction Data used by
Management
• Provide record of operations data to track
resources used and performance
• Provide record of current business functions
so management can make better decisions
using an accurate of business situation
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TPS Placement within MSS
Sales
Inventory Transaction
Processing
System
Payroll
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Organisational
Database
Management
Information
Systems
Decision
Support
Systems
Expert
Systems
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Used by
all levels of
management
and all
functional
areas
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What is a Transaction Processing
System
• Provides tools to automate and standardise the
process of recording and storing changes to the
organisational database
• Request based system that processes business
transactions
• Each transaction is processed as part of a
workflow
• Transactions-based systems are distributive by
nature and are becoming more decentralised.
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Characteristics of a TPS
• Fast and efficient processing of large amounts of
data
• Ensure accurate data records are kept
• Highly secure storage of data
• Mission critical - NO downtime
• Manual or Automated
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TPS Requirements
• Do multiple operations based on a single
transaction, i.e. log payment and update
inventory.
• Handle high volume of transactions
efficiently
• Perform concurrent transactions yet remain
consistent, i.e. book seats for a concert
without double booking a seat.
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TPS Requirements (con’t)
• Transactions run to completion before updating
database, no partially completed transactions.
• Transaction systems are scalable.
• Zero down time, most transactions are “mission
critical”.
• Transactions must be permanently stored, never
lost
• System must operate in a distributed
environment
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Critical TPS Properties “ACID”
Atomic
Consistent
Isolated
Durable
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Transaction executes completely
o r n o t a t a l l.
Transaction preserves the
internal consistency of the
database.
Transaction executes as if it
were running alone, with no
effect caused by other
transactions.
Transaction results are not lost
in case of computer system
failure.
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Transaction States
• Start
– Transaction process has started
• Commit
– Transaction process has completed with no
errors
• Abort
– Transaction process has stopped due to an error
or failure
– No partial processing is saved after, records are
stored in state prior to abort
* All Systems must have Transaction Reversal Procedure
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ACID Examples
TPS System Components
• Hardware :
:
:
• Software :
:
:
:
:
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Computers/Terminals
Servers/Workstations/Mainframes
LAN/WAN/Switches/Routers
User Interface/GUI/Windows 95
Application/Web pages
TP Monitor Programme
Communications Management Programme
TP Application Programmes
DBMS
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TPS Systems View
T
P
M
o
n
I
t
o
r
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Data
Resource
Data
Resource
Data
Resource
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TPS Components
Manages &
Coordinates flow
of transactions
thru system
Basic Electronic
& Physical
Manages
Communication
Network (LAN)
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TP
Monitor
User
Interface
Security
Operating
System
Network
Manager
Applications
Tools
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DBMS
Keyboard,
Scanner
Runs
Computer/WS
under
TP Monitor
Stores
Completed
Transactions
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TP Monitor System View
Presentation Manager
LAN/WAN
Workflow Controller
Transaction Programme
Database System
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CLIENT
Distributed System
SERVER
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TP Monitor Architecture
Presentation
Server
Terminal
Transaction
Server 1
Database 1
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Network Interface
Workflow
Controller
Transaction
Server 2
Database 2
•••
•••
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Transaction
Server N
Database N
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Presentation Manager/Server
• Takes input from user and translates into TP
Monitor readable format (Presentation
Independence)
User Interface
Reads icon clicks, menu pull downs
Produces correct form for user
Reads input data from form/Validates Data
Translates Input to TP Standard Request
Request Conductor
Translates Output to Device readable
Requests to
message
Workflow Controller
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Workflow Controller
• Functions
– Maps request type to particular Transaction Server
programme using Business Rules
– Routes request to appropriate Transaction Server
– Routes response to request to Presentation Server
– Issues Start, Commit and Abort operations
• Architecture
– May be connected to several Presentation Servers and
Transaction Servers
• Exception Handling (Failure Recognition/Action)
– Transaction Failure
– System Failure
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Transaction Server
• Special purpose programmes on special
purpose servers (or partitioned workstation)
• Transaction Application Programmes
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Written in C, C++ or COBOL
Interfaces with SQL generated databases
Designed for high request rate
Designed for transaction based communication
Modular Design
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Bank Account Example
Presentation
Server 1
Presentation
Server 2
Workflow
Controller
Transaction
Server (Customers)
Accounts
1-19,999
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Transaction
Server (Accounts)
1. Menu items and forms to open
customer account
Translate user input to standard
Request
2. Determine a new account must be
opened and send appropriate request
to Customer and Accounts Servers
(Business Rules)
Accounts
20,000 - 39,999
3. Customer Server creates
new customer. Accounts
Server creates a new account
and determines starting balance
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TPS Updates
• Batch Processing
– Accumulation of period’s transactions and
update database at the end of the period.
• On-line Processing
– Data sent after entry to a central processor for
updating. Database updated after every
transaction.
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TPS Applications
• First Large Scale TPS SABRE
– Reservation system developed by American
Airlines and IBM
– Transactions: Make a booking, change a
booking, seat allocation, change day/time…
– 300,000 devices connected, 42,000
simultaneous requests
• TPS new frontier
– World Wide Web and Electronic Data
Interchange Victoria University of Wellington
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Transactions over Internet
•TP Monitor design ideal for Internet (dynamic pages)
•Distributed nature
•Scalability
Presentation Server
Web Browser http
html
Workflow Controller
TP Monitor
Daemon
Client
Messages Written
in HyperText
Markup Language
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Organisation TP
System
Presentation Server
Workflow Controller
Organisational
Database
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Database System Recovery
• Failure recovery
– quickly return to a known state
– include all committed transactions
– exclude all aborted transactions
• Failure types
– transaction failure - transaction aborts
– system failure - HD failure/corruption, OS
failure
– media failure - any part of the stable storage is
destroyed.
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TPS Disaster Recovery Planning
• Issues
– Maintaining Corporate Transaction data
– Keep processing transactions until return to normal
operations
• Recovery
– Implementation of Disaster Plan
• Components of Disaster Plan
– Hardware/Software/Database Backup
– Rerouting telecommunications functions
– Personnel available 24 hours a day for
recovery/implementation
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Example Problem
• Describe transactions for buying a concert
ticket
• What databases are accessed?
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