Explain the principle of working of synchronous data replication in database management systems.

Serialization level (Serializable) is the strictest transaction isolation level in RDBMS. Its role is to guarantee that concurrent transaction execution is equivalent to some sequential (one after another) execution. This prevents phenomena like phantom reads, dirty reads, and non-repeatable reads.

In practice, this means transactions cannot see intermediate changes of other transactions and cannot conflict when modifying the same data. As a result, maximum data integrity is achieved, but performance may decrease due to locks and waits.

Example in PHP with PDO to set the isolation level:

$pdo->exec("SET TRANSACTION ISOLATION LEVEL SERIALIZABLE");
$pdo->beginTransaction();
// database operations
$pdo->commit();