Concurrency Problems and Transaction Terms

Question 1

Lost Update

Answer 1

Lost Update: Occurs when two transactions read the same data simultaneously, and both update the data independently. The second update overwrites the changes made by the first transaction, leading to the loss of the initial update.

Question 2

commit

Answer 2

Commit: Finalizes a transaction, making all its changes permanent in the database. Once committed, the changes are durable and survive system failures.

Question 3

rollback

Answer 3

Rollback: Undoes the changes made by a transaction, reverting the database to its state before the transaction began. Used to discard changes if an error occurs or to ensure the Atomicity property.

Question 4

write-ahead transaction log

Answer 4

Write-Ahead Transaction Log: A mechanism where changes made by a transaction are first recorded in a log before being applied to the database. This ensures durability by allowing for recovery in case of system failures.