In ACID, what does Isolation guarantee?
Options
- Data survives crashes and power failures
- Concurrent transactions behave as if run in some serial order (Correct option)
- Transactions are all-or-nothing, never partially applied
- Constraints are always satisfied after each transaction
Answer
Concurrent transactions behave as if executed in some serial order (to the degree of the chosen isolation level)
Why
ACID are four guarantees of database transactions:
- Atomicity: all or nothing.
- Consistency: rules and constraints always hold.
- Isolation: transactions running at the same time do not see each other's half-finished work.
- Durability: once committed, data survives a crash.
Isolation has levels: stricter levels are safer but slower.
Remember
Isolation = concurrent transactions don't step on each other.