Transaction Processing Systems Overview
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Questions and Answers

What defines a serial schedule in transaction processing?

  • Operations can interleave without restrictions.
  • A transaction can start before another ends.
  • All transactions must complete simultaneously.
  • Transactions are executed one after the other. (correct)

    • How many different serial schedules can be created for a set of n transactions?

  • $n^2$
  • $2^n$
  • $n + 1$
  • $n!$ (correct)

    • Which of the following is not a condition for operations to conflict in a schedule?

  • They belong to different transactions.
  • They access the same item.
  • At least one operation is a write operation.
  • They access different items. (correct)

    • What is required for a schedule to be considered complete?

    <p>It includes a commit or abort operation for each transaction.</p> Signup and view all the answers

    What is considered a logical unit of database processing that must be completed in its entirety?

    <p>Transaction</p> Signup and view all the answers

    In a complete schedule, what must be preserved among operations from the same transaction?

    <p>Their relative order of appearance must be the same.</p> Signup and view all the answers

    What type of system allows multiple users to access the database simultaneously?

    <p>Multi-user system</p> Signup and view all the answers

    What does it mean for one conflicting operation to occur before another in a schedule?

    <p>At least one operation must be a write operation.</p> Signup and view all the answers

    Which of the following best describes transaction processing systems?

    <p>Systems with large databases and high user concurrency</p> Signup and view all the answers

    Which of the following descriptions best represents conflicting operations?

    <p>Operations that write to the same item from different transactions.</p> Signup and view all the answers

    What is a characteristic of multi-programming in database systems?

    <p>Allows simultaneous execution of multiple programs</p> Signup and view all the answers

    Which of the following is a characteristic of serial schedules?

    <p>They guarantee isolation of transactions.</p> Signup and view all the answers

    In the context of database systems, what is the primary difference between single-user and multi-user systems?

    <p>The number of concurrent users using the system</p> Signup and view all the answers

    What is one of the main requirements for transaction processing systems?

    <p>High availability</p> Signup and view all the answers

    Which of the following is NOT a typical application of transaction processing systems?

    <p>Video streaming</p> Signup and view all the answers

    What does the criterion for classifying a database system depend on?

    <p>Number of users accessing the system concurrently</p> Signup and view all the answers

    What does atomicity ensure in a transaction?

    <p>A transaction is processed only if all operations are successful.</p> Signup and view all the answers

    Which of the following best describes the consistency property of transactions?

    <p>The database must remain consistent throughout the entire transaction.</p> Signup and view all the answers

    What is the main benefit of isolation in transactions?

    <p>It allows concurrent transaction execution without interference.</p> Signup and view all the answers

    In the atomicity of transactions, what happens if one part of a transaction fails?

    <p>The entire transaction is rolled back to maintain integrity.</p> Signup and view all the answers

    When referring to the consistency property, what must be true after a transaction completes?

    <p>The total of A and B must remain the same before and after.</p> Signup and view all the answers

    How does isolation affect the execution of transactions?

    <p>It allows transactions to run concurrently without visibility to each other.</p> Signup and view all the answers

    Which situation best illustrates a violation of atomicity?

    <p>A transaction deducts money from one account but fails to credit another.</p> Signup and view all the answers

    What is an implication of having multiple transactions executing concurrently?

    <p>Each transaction should appear isolated from others.</p> Signup and view all the answers

    What does the DBMS ensure regarding concurrent schedules?

    <p>All concurrent schedules are recoverable.</p> Signup and view all the answers

    What is the result of the schedule 'Sc: r1(X); w1(X); r2(X); r1(Y); w2(X); c2; a1'?

    <p>Not recoverable</p> Signup and view all the answers

    What is cascading rollback?

    <p>Rolling back uncommitted transactions that read from failed transactions.</p> Signup and view all the answers

    What defines a cascadeless schedule?

    <p>Only committed reads are allowed in the schedule.</p> Signup and view all the answers

    Why is it important to characterize schedules to avoid cascading rollback?

    <p>Because cascading rollback can be costly and time-consuming.</p> Signup and view all the answers

    What happens to uncommitted transactions during a cascading rollback?

    <p>They must be rolled back if they read from failed transactions.</p> Signup and view all the answers

    What is one potential consequence of a transaction abort?

    <p>Significant rework might still be necessary.</p> Signup and view all the answers

    Which of the following is an example of a transaction operation?

    <p>writing to a database</p> Signup and view all the answers

    What characterizes a serial schedule?

    <p>Operations of each transaction are executed consecutively without interleaving.</p> Signup and view all the answers

    What is the main issue with serial schedules?

    <p>They can lead to wasted CPU processing time.</p> Signup and view all the answers

    Which type of schedule ensures that transactions can execute without interference and produce a database state equivalent to that of a serial schedule?

    <p>Conflict Serializable Schedule</p> Signup and view all the answers

    What does conflict serializability depend on?

    <p>Access patterns of transactions that include data modifications.</p> Signup and view all the answers

    In a non-serial schedule, what is a primary characteristic?

    <p>Transactions are interleaved, with operations from different transactions mixed.</p> Signup and view all the answers

    What must occur for two transactions to force an order upon one another in conflict serializability?

    <p>At least one transaction must change the data being accessed.</p> Signup and view all the answers

    How can the results of non-conflicting operations in a schedule be affected by their order?

    <p>The results will always remain the same regardless of their order.</p> Signup and view all the answers

    Which of the following is NOT a type of equivalence that leads to different kinds of serializability?

    <p>Shared Serializability</p> Signup and view all the answers

    Study Notes

    Transaction Processing Systems

    • Large databases with hundreds of concurrent users
    • Examples: airline reservations, banking, credit card processing, online retail purchasing, stock markets, supermarket checkouts
    • High availability and fast response time are essential
    • Transaction: Logical unit of database processing, must complete entirely for correctness

    Transaction States

    • Atomicity: A transaction is treated as a single unit; either all operations are executed, or none.
      • Example: Transferring money between accounts - either both debit and credit happen, or neither does.
    • Consistency: Database must remain consistent after a transaction.
      • If the database was consistent before the transaction, it must stay consistent after the transaction completes.
      • Temporary inconsistencies may occur during the transaction execution.
    • Isolation: Each transaction is unaware of other concurrent transactions.
      • Intermediate transaction results are hidden from others.
      • Transactions appear to execute sequentially, although they may run concurrently.
    • Durability: Changes made by a successfully completed transaction are permanently stored in the database.

    Schedules & Serializability

    • Serial Schedule: Transactions execute one after another, no interleaving.
      • N transactions have N! possible serial schedules.
    • Conflicting Operations: Occur when two operations from different transactions:
      • Access the same item.
      • At least one operation is a write operation.
    • Complete Schedule: Includes all operations from all transactions, with commit or abort as the final operation for each.
    • Conflict Serializability: A concurrent schedule is equivalent to a serial schedule in terms of conflicting operations.
    • View Serializability: A schedule is equivalent to a serial schedule in terms of the final values of data items.

    Recovery Concepts

    • Recoverability: Ensures that all concurrent schedules are recoverable.
      • Guarantees successful transaction commits are reflected in the database.
      • Rollback of aborted transactions.
    • Cascading Rollback (Cascading Abort): An uncommitted transaction must rollback because it read data from a failed transaction.
      • Can be costly and time-consuming.
    • Cascadeless Schedule: Avoids cascading rollback.
      • Each transaction only reads data written by committed transactions.
      • Guarantees that a failed transaction will not cause other transactions to rollback.

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    Related Documents

    BCSE302L DBMS Module 5 PDF

    Description

    This quiz covers the fundamentals of Transaction Processing Systems, focusing on their importance in handling large databases with concurrent users. It delves into key concepts such as atomicity, consistency, and isolation, which are essential for ensuring data integrity during transactions.

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