Q.State the four ACID properties of a transaction and write one line on each.

ACID lists the four guarantees that make a transaction reliable; this asks you to name and briefly explain each.

The reliability of database transactions is summed up by four properties, remembered by the letters ACID:

1. Atomicity — a transaction is 'all-or-nothing': every statement in it takes effect, or none does. ROLLBACK provides this.
2. Consistency — a transaction takes the database from one valid state to another valid state, never leaving it half-changed or breaking its rules (constraints).
3. Isolation — when several transactions run at the same time, each behaves as if it were running alone; they do not interfere with one another's intermediate changes.
4. Durability — once a transaction is committed, its changes are permanent and survive even a power failure or system crash. COMMIT provides this.
   ✓Final answer

   Atomicity — all statements of a transaction happen or none do; Consistency — the database goes from one valid state to another; Isolation — concurrent transactions do not interfere with each other; Durability — once committed, changes are permanent even after a failure.

Do not confuse Consistency with Isolation: consistency is about the data staying valid, isolation is about concurrent transactions not disturbing each other. Link Atomicity to ROLLBACK and Durability to COMMIT to remember them.