Isolation levels mengontrol seberapa banyak transaksi konkuren dapat melihat perubahan uncommitted (atau in-progress) satu sama lain — melakukan trade-off antara consistency dan performance/concurrency. Isolasi yang lebih tinggi mencegah lebih banyak anomali tetapi meningkatkan locking/contention.
Anomali concurrency (apa yang isolasi cegah)
DIRTY READ → reading another transaction's UNCOMMITTED changes (which may roll back)
NON-REPEATABLE READ → re-reading a row gives different values (another txn UPDATED it)
PHANTOM READ → re-running a query returns different ROWS (another txn INSERTED/DELETED)
