seriellserialiserbar

seriellserialiserbar is a term used in database theory to describe a property of a concurrent execution of multiple transactions. A schedule (the interleaving of operations from several transactions) is seriellserialiserbar if its effect on the database is the same as if the transactions had been executed in some serial order, one after another, without interleaving.

There are different notions of seriellserialiserbarhet. The most common are conflict-serializability and view-serializability. Conflict-serializability relies on conflicts between operations (such as read-write or write-write on the same data item). A schedule is conflict-serializable if it is equivalent to a serial schedule with respect to these conflicts. View-serializability is a weaker notion: a schedule is view-serializable if its read and write effects can be aligned with some serial order, even if not all conflicts match in a way that conflict-serializability requires. Every conflict-serializable schedule is view-serializable, but not every view-serializable schedule is conflict-serializable.

Checking seriellserialiserbarhet often involves a formal mechanism such as a precedence graph (also called a conflict graph). In this graph, nodes represent transactions and directed edges indicate that one transaction’s operation on a data item precedes a conflicting operation of another. If this graph contains a cycle, the schedule is not conflict-serializable and hence not seriellserialiserbar. If the graph is acyclic, the schedule is conflict-serializable and therefore seriellserialiserbar.

Concurrency control techniques aim to enforce seriellserialiserbarhet. Two-phase locking (2PL), including strict 2PL, is a common approach that guarantees serializability. Other protocols like timestamp ordering can also ensure seriellserialiserbarhet under different assumptions. In practice, seriellserialiserbarhet provides a strong correctness guarantee for concurrent transactions, while allowing controlled parallelism to improve performance.