Ultimate goal

The final database state must be correct

(as if transactions ran one-by-one in some order)

This is final-state / serial correctness.

But reality

• Transactions arrive concurrently
• DB cannot foresee future operations
• DB cannot enumerate all schedules
• DB must decide dynamically, step by step

So the DB must:

• Allow concurrency (performance)
• While guaranteeing correctness (safety)

Prevent bad schedules from forming on the fly , instead of detecting them later(as that would be costly and also some side effects may have happened in app logic based on received states)

final state serializabilty can happen wiuthout enforcing conflict serializability but conflict ser enfocrces final state ser

even cyclic can be conflict serializable but acyclic enforces conflict ser

A️⃣ Lock-based (2PL family)

“If two operations would conflict, don’t let them overlap.”