Concurrency Control in Database Management
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Questions and Answers

What are the three closely related functions intended to ensure database reliability and consistency?

  • Data retrieval, data storage, and data deletion
  • Transaction support, concurrency control services, and recovery services (correct)
  • Indexing, sorting, and filtering
  • Data modeling, data manipulation, and data security

    • What is the process of restoring the database to a correct state following a failure?

  • Database normalization
  • Database optimization
  • Database recovery (correct)
  • Data migration

    • What is a Transaction in the context of database management?

  • A system crash due to hardware errors
  • An action carried out by a single user or application program that reads or updates the contents of the database (correct)
  • A logical error in the program that is accessing the database
  • A scheduled task for database maintenance

    • What is the purpose of a concurrency control protocol in a DBMS?

    <p>Prevents database accesses from interfering with one another</p> Signup and view all the answers

    What does database recovery aim to achieve in the event of a failure?

    <p>Restore the database to a consistent state</p> Signup and view all the answers

    What is a schedule in the context of transaction management?

    <p>A sequence of operations by concurrent transactions preserving individual transaction order</p> Signup and view all the answers

    Why is the order of read and write operations crucial for serializability?

    <p>It affects the ability to maintain consistency and avoid interference between transactions</p> Signup and view all the answers

    What is used to test for conflict serializability?

    <p>Precedence graph</p> Signup and view all the answers

    What is the purpose of recoverability in transaction management?

    <p>To examine the ability to undo transaction effects and maintain changes after commit</p> Signup and view all the answers

    What does locking ensure in concurrent transactions?

    <p>The serializability of concurrent transactions</p> Signup and view all the answers

    What is the main objective of developing a database in the context of concurrency control?

    <p>To enable many users to access shared data concurrently</p> Signup and view all the answers

    Which problem occurs when a transaction reads values from the database and another transaction updates some of them, leading to inaccurate results?

    <p>Inconsistent analysis problem</p> Signup and view all the answers

    What is the main aim of concurrency control protocols?

    <p>To schedule transactions to avoid interference and prevent problems</p> Signup and view all the answers

    What is the significance of interleaved operations of transactions in achieving concurrent execution?

    <p>It helps achieve concurrent execution and improve throughput</p> Signup and view all the answers

    What is the lost update problem in the context of concurrency control?

    <p>When one user's update operation is overridden by another user</p> Signup and view all the answers

    What is the purpose of the recovery manager in database architecture?

    <p>To restore the database to a consistent state after a failure</p> Signup and view all the answers

    What are the ACID properties that all transactions should possess?

    <p>Atomicity, Consistency, Isolation, and Durability</p> Signup and view all the answers

    What is the role of concurrency control in database management?

    <p>Managing simultaneous operations on the database without interference</p> Signup and view all the answers

    What is the primary purpose of exclusive locks in transaction management?

    <p>Preventing both read and update access by other transactions</p> Signup and view all the answers

    What happens to committed transactions in a database?

    <p>They cannot be aborted and result in reaching a new consistent state</p> Signup and view all the answers

    In two-phase locking (2PL) protocol, what is the purpose of the shrinking phase?

    <p>Releasing locks without acquiring new ones</p> Signup and view all the answers

    What is the primary function of the transaction manager in database architecture?

    <p>To coordinate transactions</p> Signup and view all the answers

    What is the potential consequence of a transaction causing a series of rollbacks known as cascading rollback?

    <p>Inconsistent database state</p> Signup and view all the answers

    How can lock contention manifest in index structures?

    <p>Frequent access leading to conflicts at higher levels of trees</p> Signup and view all the answers

    When are locks explicitly released in transaction management?

    <p>During execution or when the transaction terminates</p> Signup and view all the answers

    What is the purpose of two-phase locking (2PL) protocol?

    <p>To acquire locks in a growing phase and release locks in a shrinking phase</p> Signup and view all the answers

    What is the consequence of a single transaction causing a series of rollbacks?

    <p>Cascading rollback</p> Signup and view all the answers

    How is lock contention managed in index structures?

    <p>By treating each index page as a data item and applying the two-phase locking protocol</p> Signup and view all the answers

    What is the potential consequence of being unable to acquire new locks during lock upgrade or downgrade?

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

    What must transactions do before accessing data items?

    <p>Lock the data items explicitly</p> Signup and view all the answers

    What is the purpose of the growing phase in the two-phase locking (2PL) protocol?

    <p>To acquire locks for data items</p> Signup and view all the answers

    What is the primary function of shared locks in transaction management?

    <p>Allow reading but not updating of a data item</p> Signup and view all the answers

    What does the shrinking phase in two-phase locking (2PL) protocol involve?

    <p>Releasing locks for data items</p> Signup and view all the answers

    What is the potential consequence of failing to acquire new locks during lock upgrade or downgrade?

    <p>Livelock occurrence</p> Signup and view all the answers

    How can concurrency control be managed for index structures?

    <p>Treating each index page as a data item and applying the two-phase locking protocol</p> Signup and view all the answers

    Study Notes

    Transaction Management and Locking Protocols

    • Locks prevent other transactions from modifying or reading a data item, with exclusive locks providing both read and update access.
    • Shared locks allow reading but not updating of a data item, and the size of the item determines the granularity of the lock.
    • More than one transaction can hold shared locks, but exclusive locks give exclusive access to the item.
    • Transactions must lock data items before accessing them, and locks must be explicitly released during or after the transaction.
    • Two-phase locking (2PL) protocol involves a growing phase for acquiring locks and a shrinking phase for releasing locks, with no new locks acquired after release.
    • A single transaction causing a series of rollbacks is called cascading rollback, which can be prevented with rigorous 2PL or strict 2PL.
    • Deadlock can occur with two-phase locking, requiring a deadlock detection and recovery scheme.
    • Concurrency control for index structures can be managed by treating each index page as a data item and applying the two-phase locking protocol.
    • Lock contention may occur with index structures due to frequent access, particularly at higher levels of trees.
    • Transactions can upgrade or downgrade locks, with the possibility of livelock if unable to acquire new locks.
    • Locks are used to request shared or exclusive access to data items, and any transaction that needs to access a data item must first lock it.
    • Locks are released explicitly during execution or when the transaction terminates, and some systems permit lock upgrades or downgrades.

    Transaction Management and Locking Protocols

    • Locks prevent other transactions from modifying or reading a data item, with exclusive locks providing both read and update access.
    • Shared locks allow reading but not updating of a data item, and the size of the item determines the granularity of the lock.
    • More than one transaction can hold shared locks, but exclusive locks give exclusive access to the item.
    • Transactions must lock data items before accessing them, and locks must be explicitly released during or after the transaction.
    • Two-phase locking (2PL) protocol involves a growing phase for acquiring locks and a shrinking phase for releasing locks, with no new locks acquired after release.
    • A single transaction causing a series of rollbacks is called cascading rollback, which can be prevented with rigorous 2PL or strict 2PL.
    • Deadlock can occur with two-phase locking, requiring a deadlock detection and recovery scheme.
    • Concurrency control for index structures can be managed by treating each index page as a data item and applying the two-phase locking protocol.
    • Lock contention may occur with index structures due to frequent access, particularly at higher levels of trees.
    • Transactions can upgrade or downgrade locks, with the possibility of livelock if unable to acquire new locks.
    • Locks are used to request shared or exclusive access to data items, and any transaction that needs to access a data item must first lock it.
    • Locks are released explicitly during execution or when the transaction terminates, and some systems permit lock upgrades or downgrades.

    Transaction Management and Locking Protocols

    • Locks prevent other transactions from modifying or reading a data item, with exclusive locks providing both read and update access.
    • Shared locks allow reading but not updating of a data item, and the size of the item determines the granularity of the lock.
    • More than one transaction can hold shared locks, but exclusive locks give exclusive access to the item.
    • Transactions must lock data items before accessing them, and locks must be explicitly released during or after the transaction.
    • Two-phase locking (2PL) protocol involves a growing phase for acquiring locks and a shrinking phase for releasing locks, with no new locks acquired after release.
    • A single transaction causing a series of rollbacks is called cascading rollback, which can be prevented with rigorous 2PL or strict 2PL.
    • Deadlock can occur with two-phase locking, requiring a deadlock detection and recovery scheme.
    • Concurrency control for index structures can be managed by treating each index page as a data item and applying the two-phase locking protocol.
    • Lock contention may occur with index structures due to frequent access, particularly at higher levels of trees.
    • Transactions can upgrade or downgrade locks, with the possibility of livelock if unable to acquire new locks.
    • Locks are used to request shared or exclusive access to data items, and any transaction that needs to access a data item must first lock it.
    • Locks are released explicitly during execution or when the transaction terminates, and some systems permit lock upgrades or downgrades.

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    Related Documents

    CIS 9340 Chapter 22 - Transaction Management PDF

    Description

    Test your knowledge of managing simultaneous operations on a database without interference. Explore the need for concurrency control and the challenges of enabling multiple users to access shared data concurrently.

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