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 (B)</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 (D)</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 (B)</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 (A)</p> Signup and view all the answers

What is used to test for conflict serializability?

<p>Precedence graph (B)</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 (C)</p> Signup and view all the answers

What does locking ensure in concurrent transactions?

<p>The serializability of concurrent transactions (D)</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 (A)</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 (D)</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 (C)</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 (B)</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 (B)</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 (D)</p> Signup and view all the answers

What are the ACID properties that all transactions should possess?

<p>Atomicity, Consistency, Isolation, and Durability (C)</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 (A)</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 (B)</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 (B)</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 (B)</p> Signup and view all the answers

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

<p>To coordinate transactions (A)</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 (C)</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 (D)</p> Signup and view all the answers

When are locks explicitly released in transaction management?

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

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

<p>Cascading rollback (A)</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 (A)</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 (D)</p> Signup and view all the answers

What must transactions do before accessing data items?

<p>Lock the data items explicitly (A)</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 (B)</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 (A)</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 (A)</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 (A)</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 (D)</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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