BE - Database Management Systems

when multiple transactions execute concurrently, the system must ensure that the outcome is correct and consistent.

One way to check correctness is through serializability, which means that the concurrent execution of transactions should be equivalent to some serial execution (i.e., transactions running one after another). Among the different types of serializability, view serializability is an important one.

A schedule is said to be view serializable if it is view equivalent to some serial schedule. Two schedules are view equivalent if three conditions are satisfied:

(1) For every read operation, the value read in both schedules must come from the same write operation;

(2) The final write in both schedules must be performed by the same transaction; and

(3) The initial reads must read the same initial values. Unlike conflict serializability,

which checks for conflicts between operations, view serializability is a broader concept because all conflict serializable schedules are also view serializable, but the reverse is not always true. However, testing for view serializability is more complex and less efficient compared to conflict serializability, which is why in practice, DBMSs mostly enforce conflict serializability.