1 / 18

Transaction I

Transaction I. Outline. Transaction and OLTP Designed properties of transactions. Transaction. A multi-billion dollar business OLTP http://www.tpc.org/default.asp . Transaction Definition. A unit of program execution that accesses and possibly updates various data items Transactions?

miyoko
Télécharger la présentation

Transaction I

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Transaction I Yan Huang - CSCI5330 Database Implementation –Transaction

  2. Outline • Transaction and OLTP • Designed properties of transactions Yan Huang - CSCI5330 Database Implementation –Transaction

  3. Transaction • A multi-billion dollar business • OLTP • http://www.tpc.org/default.asp Yan Huang - CSCI5330 Database Implementation –Transaction

  4. Transaction Definition • A unit of program execution that accesses and possibly updates various data items • Transactions? • Book an airline ticket from DFW to Paris • Buy “The Dilbert Principle” from amazon.com • Sell 1000 shares of LU from your ameritrade account • Withdraw $100 from a ATM machine • Issue a SQL statement to sqlplus of Oracle 9i • Look at your grade of homework 3 • Check out your groceries at Walmart Yan Huang - CSCI5330 Database Implementation –Transaction

  5. Challenges to Maintain Transactions • Hardware failures • Cashed stuck in ATM machine • Power failure… • Software failures • Programming errors • System crash… • User interference • Termination of transactions • Concurrent users • Multiple users accessing the same item Yan Huang - CSCI5330 Database Implementation –Transaction

  6. Designed Properties of Database Systems • Atomicity • Consistency • Isolation • Durability Yan Huang - CSCI5330 Database Implementation –Transaction

  7. Atomicity • Transaction needs to be executed as a unit • Example • You should not cause the quantity of “The Dilbert Principle” of amazon.com decrease if you place your order and the order does not get through due to server errors • Who are responsible for atomicity? • Transaction management system and • Recovery system Yan Huang - CSCI5330 Database Implementation –Transaction

  8. Consistency • Database implicit/explicit constraints need to be maintained • Example: • Transferring money from one account to another in the same bank should not change your total amount of money • Who are responsible for consistency? • Transaction management system and • Programmer Yan Huang - CSCI5330 Database Implementation –Transaction

  9. Isolation • Transaction A should not see partial results of transaction B • Analogy: • When I update my website here and there, you should not see and think a tentative version as my final version • Who are responsible for isolation? • Transaction management system Yan Huang - CSCI5330 Database Implementation –Transaction

  10. Durability • Any transaction committed needs to be in database for ever • Example: • After you get the receipt of the water melon you buy from Alberson, the transaction is final and permanently reflected in the database system • If you want to cancel it, that is another transaction • Who are responsible for durability? • Transaction management system and • Recovery system Yan Huang - CSCI5330 Database Implementation –Transaction

  11. Transaction’s State Diagram Yan Huang - CSCI5330 Database Implementation –Transaction

  12. An Ideal World • No hardware failures • No software failures • No programming errors • Do we still need transaction management? Yan Huang - CSCI5330 Database Implementation –Transaction

  13. Why Concurrent Transactions? • Parallelism • Improved response time Yan Huang - CSCI5330 Database Implementation –Transaction

  14. Schedule • Schedules – sequences that indicate the chronological order in which instructions of concurrent transactions are executed • a schedule for a set of transactions must consist of all instructions of those transactions • must preserve the order in which the instructions appear in each individual transaction. Yan Huang - CSCI5330 Database Implementation –Transaction

  15. Example Schedules Yan Huang - CSCI5330 Database Implementation –Transaction

  16. Example Schedule (Cont.) Yan Huang - CSCI5330 Database Implementation –Transaction

  17. Example Schedules Yan Huang - CSCI5330 Database Implementation –Transaction

  18. Concurrency Control • Some schedules are bad because the outcome of the schedule is not “predictable” Yan Huang - CSCI5330 Database Implementation –Transaction

More Related