Saturday, November 18, 2017

Define serializability in database transaction management

Define serializability in database transaction management, what is serializability, serializable schedules, when would we say that a schedule is serializable


As we know, we cannot execute all transactions only in serial order as it will consume enormous amount of time and resources. Hence, an RDBMS need to permit concurrent transactions (transactions that are executed simultaneously).
Execution of a collection of multiple transactions together is called as schedule. And, a schedule either should be serial or serializable.
To ensure database consistency, a database system must control execution of concurrent transactions. In other words, the system must identify whether a schedule produces consistent database or not.
How do we check whether a schedule produces consistent database or not?
A schedule of concurrent transactions ends in a consistent database if the schedule is equivalent to some serial schedule.
If a schedule of concurrent transactions can be converted into an equivalent serial schedule, then we say that the schedule is serializable schedule. And this property is called serializability.

The concept of serializability of schedules is used to identify which schedules are correct when transaction executions have interleaving of their operations in the schedules. There are different notions of schedule equivalences. The following are two of the important equivalence of schedules;

  • View serializability



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