dbms transaction processing concepts

Transaction processing concepts

A transaction is a unit of program execution that accesses and  possibly updates one or more data items in  the database.

For example,

Money transfer from an account to another account.

Transaction to transfer Rs 1000 from account A to account B:
  1. Read(A)
  2. A := A – 500
  3. Write(A)
  4. Read(B)
  5. B := B + 500
  6. Write(B)
Two main issues to deal in transaction:
  1. Failures of various kinds, such as hardware failures and system crashes
  2. Concurrent execution of multiple transactions
A transction must follow ACID properties.

Acid properties:

  1. Atomicity
  2. Consistency
  3. Isolation
  4. Durability
1) Atomicity.  Either all operations of the transaction are properly reflected in the database or none are.
2) Consistency.  Execution of a transaction in isolation preserves the consistency of the database.
3) Isolation.  Although multiple transactions may execute concurrently, each transaction must be unaware of other concurrently executing transactions.
4) Durability.  After a transaction completes successfully, the changes it has made to the database persist, even if there are system failures.

Transaction states:

1. Active, the initial state; the transaction stays in this state while it is executing
2. Partially committed, after the final statement has been executed.
3. Failed, after the discovery that normal execution can no longer proceed.
4. Aborted, after the transaction has been rolled back and the database restored to its state prior to the start of the transaction.  
Two options after it has been aborted:
  • restart the transaction – only if no internal logical error
  • kill the transaction
5. Committed, after successful completion.


Check this video lecture on Transaction processing system.

Python Programming ↓ 👆
Java Programming ↓ 👆
JAVA EasyExamNotes.com covered following topics in these notes.
JAVA Programs
Principles of Programming Languages ↓ 👆
Principles of Programming Languages
EasyExamNotes.com covered following topics in these notes.

Practicals:
Previous years solved papers:
A list of Video lectures References:
  1. Sebesta,”Concept of programming Language”, Pearson Edu 
  2. Louden, “Programming Languages: Principles & Practices” , Cengage Learning 
  3. Tucker, “Programming Languages: Principles and paradigms “, Tata McGraw –Hill. 
  4. E Horowitz, "Programming Languages", 2nd Edition, Addison Wesley

    Computer Organization and Architecture ↓ 👆

    Computer Organization and Architecture 

    EasyExamNotes.com covered following topics in these notes.

    1. Structure of desktop computers
    2. Logic gates
    3. Register organization
    4. Bus structure
    5. Addressing modes
    6. Register transfer language
    7. Direct mapping numericals
    8. Register in Assembly Language Programming
    9. Arrays in Assembly Language Programming

    References:

    1. William stalling ,“Computer Architecture and Organization” PHI
    2. Morris Mano , “Computer System Organization ”PHI

    Computer Network ↓ 👆
    Computer Network

    EasyExamNotes.com covered following topics in these notes.
    1. Data Link Layer
    2. Framing
    3. Byte count framing method
    4. Flag bytes with byte stuffing framing method
    5. Flag bits with bit stuffing framing method
    6. Physical layer coding violations framing method
    7. Error control in data link layer
    8. Stop and Wait scheme
    9. Sliding Window Protocol
    10. One bit sliding window protocol
    11. A protocol Using Go-Back-N
    12. Selective repeat protocol
    13. Application layer
    References:
    1. Andrew S. Tanenbaum, David J. Wetherall, “Computer Networks” Pearson Education.
    2. Douglas E Comer, “Internetworking with TCP/IP Principles, Protocols, And Architecture",Pearson Education
    3. KavehPahlavan, Prashant Krishnamurthy, “Networking Fundamentals”, Wiley Publication.
    4. Ying-Dar Lin, Ren-Hung Hwang, Fred Baker, “Computer Networks: An Open Source Approach”, McGraw Hill.