In a serializable Isolation level, transaction runs in complete isolation.
A serializable transaction operates in an environment that makes it appear as if no other users were modifying data in the application (database).
Two simultaneous transactions occurring within the database at the same time are isolated from one another. They cannot interfere with one another. Intermediate results within a transaction remain invisible to other transactions.
This is the only transaction isolation level that avoid all data problem (phenomena).
Full serializable access is guaranteed.
While this degree of isolation between transactions is generally desirable, running many applications in serializable mode can seriously compromise application throughput. Serialization devices inhibit Concurrency.