10.4.1 ACID properties

• What is a transaction in the context of databases?

  Logical unit of work
• Each transaction in a database must adhere to the ACID properties to maintain data integrity.integrity
• What does Atomicity ensure in a database transaction?

  All operations succeed or fail together
• Consistency in ACID properties ensures that a transaction moves the database from one consistent state to another.
• Isolation in ACID properties prevents one transaction from seeing changes made by another until it is committed
• What does Durability guarantee in a database transaction?

  Changes are permanent after commitment
• Steps involved in transferring money from account A to account B in a database transaction

  1️⃣ Deduct the amount from account A

  2️⃣ Add the amount to account B

  3️⃣ Commit the changes to the database
• If any step in a transaction fails, the entire transaction is rolled back to maintain consistency.
• Atomicity in ACID properties ensures all operations in a transaction complete successfully or none are executed
• What does Isolation prevent in concurrent database transactions?

  Interference between transactions
• Transferring money between accounts is an example of a transaction that ensures funds are deducted from one account and added to another.
• What happens to a bank transfer transaction if the credit to the destination account fails?

  The entire transaction is rolled back
• Isolation in ACID properties prevents concurrent transactions from interfering with each other's changes
• What happens if the credit to account B fails during a money transfer transaction?

  The debit from A is undone
• Atomicity ensures that all operations in a transaction are treated as a single, indivisible unit.
• Atomicity in database transactions ensures that all operations within a transaction are treated as a single, indivisible unit
• What is the effect of a rollback in a database transaction on the data integrity?

  Restores the database to its original state
• If a transaction fails and is rolled back, the database returns to its consistent state before the transaction began.
• In a bank transfer transaction, if the debit from account A is successful but the credit to account B fails, the transaction is rolled back
• Match the ACID property with its definition:

  Atomicity ↔️ All operations succeed or fail together

  Consistency ↔️ Database moves from one consistent state to another

  Isolation ↔️ Transactions are independent

  Durability ↔️ Changes are permanent after commitment
• Two users updating the same stock level without affecting each other is an example of Isolation.
• Atomicity in ACID properties ensures all operations in a transaction complete successfully, or none at all
• What is the primary purpose of Consistency in ACID properties?

  Preserve the database integrity
• What does atomicity ensure in database transactions?

  All or nothing
• In atomicity, every operation in a transaction must either succeed or fail together
• If a credit to account B fails during a money transfer, the debit from account A is undone.
• Match the aspect of atomicity with its definition:

  All or Nothing ↔️ Every operation succeeds or fails together

  Rollback ↔️ Reverts to the original state

  Consistency ↔️ Ensures data integrity
• What does consistency ensure in database transactions?

  Data integrity
• The total balance of all accounts remains the same before and after a consistent bank transfer.
• Consistency ensures that all database rules and constraints are satisfied
• What does isolation prevent in concurrent database transactions?

  Data corruption
• The "Read Uncommitted" isolation level prevents dirty reads.

  False
• Match the isolation level with its description:

  Read Uncommitted ↔️ Reads uncommitted data

  Read Committed ↔️ Reads only committed data

  Repeatable Read ↔️ Protects against non-repeatable reads

  Serializable ↔️ Ensures serial execution
• What does durability guarantee in database transactions?

  Permanent changes
• Write-Ahead Logging (WAL) is used to ensure durability by recording changes in a log
• Regular backups are essential for database recovery in case of system failures.