Database develop. life cycle - ACID properties

ACID properties and explain their role in the data development cycle, especially in databases and transactional systems.

ACID Properties

ACID stands for Atomicity, Consistency, Isolation, and Durability. These are the key principles that ensure reliability of database transactions (like insert, update, delete) in applications.

1. Atomicity – “All or Nothing”

Ensures that a transaction is treated as a single unit.
Either all operations within the transaction are completed successfully, or none are applied.
Example: In online banking, transferring money from Account A to Account B must debit A and credit B together. If one step fails, both should roll back.

2. Consistency – “Valid State”

Ensures that a transaction brings the database from one valid state to another valid state according to defined rules, constraints, and triggers.
No transaction should corrupt the database.
Example: If a column requires positive values (like stock quantity), the database should reject any transaction inserting a negative value.

3. Isolation – “No Interference”

Ensures that concurrent transactions do not interfere with each other.
Each transaction should behave as if it’s the only one running, even if multiple are happening simultaneously.
Example: Two customers buying the last item in stock at the same time—only one should succeed, and isolation prevents data conflicts.

4. Durability – “It Stays”

Once a transaction is committed, it is permanently stored, even if the system crashes or restarts.
Achieved using techniques like transaction logs and backups.
Example: Once your online payment is confirmed, it won’t disappear due to a server failure—the system guarantees it’s recorded.

ACID in the Data Development Cycle

Data Design Phase → Schema and constraints are defined to enforce consistency.
Development Phase → Transactions are coded with atomicity in mind, ensuring rollbacks on failure.
Testing Phase → Stress testing checks isolation to handle multiple users and operations simultaneously.
Deployment & Maintenance Phase → Database logging, replication, and backups ensure durability in production.