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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 INFO 213 Victoria University of Wellington 2 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 INFO 213 Victoria University of Wellington 3 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 INFO 213 Victoria University of Wellington 4 Business Transactions • Why do businesses have transactions – – – – INFO 213 Sell Products Exchange Goods Inform Customers Deliver Service Victoria University of Wellington 5 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 • • • • INFO 213 pay check service good loan check Victoria University of Wellington 6 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 INFO 213 Victoria University of Wellington 7 Examples of Business Transactions • • • • • • • • • Banking Securities Trading Insurance Inventory Control Manufacturing Retail Government Internet Telecommunications INFO 213 • • • • • • • • • 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 Victoria University of Wellington 8 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 INFO 213 Victoria University of Wellington 9 TPS Placement within MSS Sales Inventory Transaction Processing System Payroll INFO 213 Organisational Database Management Information Systems Decision Support Systems Expert Systems Victoria University of Wellington Used by all levels of management and all functional areas 10 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. INFO 213 Victoria University of Wellington 11 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 INFO 213 Victoria University of Wellington 12 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. INFO 213 Victoria University of Wellington 13 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 INFO 213 Victoria University of Wellington 14 Critical TPS Properties “ACID” Atomic Consistent Isolated Durable INFO 213 Transaction executes completely o r n o t a t a ll. 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. Victoria University of Wellington 15 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 INFO 213 Victoria University of Wellington 16 ACID Examples TPS System Components • Hardware : : : • Software : : : : : INFO 213 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 Victoria University of Wellington 18 TPS Systems View T P M o n I t o r INFO 213 Victoria University of Wellington Data Resource Data Resource Data Resource 19 TPS Components Manages & Coordinates flow of transactions thru system Basic Electronic & Physical Manages Communication Network (LAN) INFO 213 TP Monitor User Interface Security Operating System Network Manager Applications Tools Victoria University of Wellington DBMS Keyboard, Scanner Runs Computer/WS under TP Monitor Stores Completed Transactions 20 TP Monitor System View Presentation Manager LAN/WAN Workflow Controller Transaction Programme Database System INFO 213 Victoria University of Wellington CLIENT Distributed System SERVER 21 TP Monitor Architecture Presentation Server Terminal Transaction Server 1 Database 1 INFO 213 Network Interface Workflow Controller Transaction Server 2 Database 2 ••• ••• Victoria University of Wellington Transaction Server N Database N 22 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 INFO 213 Victoria University of Wellington 23 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 INFO 213 Victoria University of Wellington 24 Transaction Server • Special purpose programmes on special purpose servers (or partitioned workstation) • Transaction Application Programmes – – – – – INFO 213 Written in C, C++ or COBOL Interfaces with SQL generated databases Designed for high request rate Designed for transaction based communication Modular Design Victoria University of Wellington 25 Bank Account Example Presentation Server 1 Presentation Server 2 Workflow Controller Transaction Server (Customers) Accounts 1-19,999 INFO 213 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 Victoria University of Wellington 26 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. INFO 213 Victoria University of Wellington 27 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 INFO 213 28 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 INFO 213 Organisation TP System Presentation Server Workflow Controller Organisational Database Victoria University of Wellington 29 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. Victoria University of Wellington INFO 213 30 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 INFO 213 Victoria University of Wellington 31 Example Problem • Describe transactions for buying a concert ticket • What databases are accessed? INFO 213 Victoria University of Wellington 32