Database Transactions

Types of Transactions

• Atomicity: A transaction is treated as a single, indivisible unit of work. If any part of the transaction fails, the entire transaction is rolled back.
• Consistency: The transaction must leave the database in a consistent state, even if the transaction fails.
• Isolation: The transaction must be executed independently, without interference from other transactions.
• Durability: The transaction's effects must be permanent and survive even in the case of system failure.

Transaction Properties

• Idempotence: A transaction can be repeated multiple times without changing the result.
• Commutativity: The order of transactions does not affect the result.
• Serializability: The transaction's effects are equivalent to a serial execution of the individual operations.

Transaction States

• Active: The transaction is currently executing.
• Committed: The transaction has successfully completed and its effects are permanent.
• Aborted: The transaction has failed and its effects are rolled back.
• Partially Committed: The transaction has partially completed, but its effects are not yet permanent.

Transaction Control

• Commit: Confirms the transaction's effects and makes them permanent.
• Rollback: Reverses the transaction's effects and returns to the previous state.
• Savepoint: Creates a temporary checkpoint in the transaction, allowing for partial rollback.

Transaction Isolation Levels

• Read Uncommitted: Allows a transaction to read uncommitted changes made by other transactions.
• Read Committed: Ensures that a transaction only reads committed changes.
• Repeatable Read: Ensures that a transaction reads a consistent view of the data, even if other transactions are making changes.
• Serializable: Ensures that the transaction's effects are equivalent to a serial execution of the individual operations.

Types of Transactions

• A transaction is treated as a single, indivisible unit of work, ensuring atomicity.
• The transaction must leave the database in a consistent state, even if the transaction fails, ensuring consistency.
• The transaction must be executed independently, without interference from other transactions, ensuring isolation.
• The transaction's effects must be permanent and survive even in the case of system failure, ensuring durability.

Transaction Properties

• A transaction can be repeated multiple times without changing the result, known as idempotence.
• The order of transactions does not affect the result, known as commutativity.
• The transaction's effects are equivalent to a serial execution of the individual operations, known as serializability.

Transaction States

• A transaction is currently executing when it's in the active state.
• The transaction has successfully completed and its effects are permanent when it's in the committed state.
• The transaction has failed and its effects are rolled back when it's in the aborted state.
• The transaction has partially completed, but its effects are not yet permanent when it's in the partially committed state.

Transaction Control

• The commit operation confirms the transaction's effects and makes them permanent.
• The rollback operation reverses the transaction's effects and returns to the previous state.
• The savepoint operation creates a temporary checkpoint in the transaction, allowing for partial rollback.

Transaction Isolation Levels

• The read uncommitted isolation level allows a transaction to read uncommitted changes made by other transactions.
• The read committed isolation level ensures that a transaction only reads committed changes.
• The repeatable read isolation level ensures that a transaction reads a consistent view of the data, even if other transactions are making changes.
• The serializable isolation level ensures that the transaction's effects are equivalent to a serial execution of the individual operations.