Practical 11

1. A transaction is an action or series of actions carried out by the user or application, which reads or updates the database content. This is important to keep consistency and maintain database integrity within the DBMS.

2. ACID stands for 4 basic properties

Atomicity – ‘All or nothing’ property

Consistency – Must transform the database from one consistent state to another.

Isolation – Partial effects of incomplete transactions should not be visible to other transactions.

Durability – Effects of a commited transaction are permanent and must not be lost because of a later failure.
These 4 properties relate to the concurrency control and recovery mechanisms by

3. If two or more people are editing the database and insert 2 transactions, this may or may not produce an incorrect result due to interleaving of operations although the transaction may be correct on its own.

4. The types of failure that can occur in a database are
Errors and failures
User error
Statement failure
Process failure
Network failure
Database instance failure
Recovery from instance failure
5.