Consider the following two statements about database transaction sched...
Strict 2 phase locking protocol ensures conflict serializability as well as strict recoverability.
So statement I is correct.
Thomas write rule sometimes discard the operation in case of multiple write and it is similar to view serializability, focus on last write.
So statement-II is also correct.
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Consider the following two statements about database transaction sched...
Strict Two-Phase Locking Protocol:
Strict two-phase locking protocol ensures that transactions follow a strict two-phase locking protocol, where all locks are acquired before any are released. This protocol generates conflict serializable schedules, meaning that the final result of executing transactions is equivalent to some serial execution of the transactions. Additionally, schedules generated using this protocol are also recoverable, ensuring that the system can recover to a consistent state in case of failures.
Timestamp-Ordering Concurrency Control Protocol with Thomas Write Rule:
The timestamp-ordering concurrency control protocol with Thomas Write Rule uses timestamps to determine the order in which transactions are executed. This protocol can generate view serializable schedules, where the final result of executing transactions is equivalent to some serial execution of the transactions that respects the read and write dependencies. However, it is possible for schedules generated using this protocol to not be conflict serializable, meaning that they may allow for conflicting operations to be executed in an order that violates the serializability property.
Conclusion:
The given statements are both true. Strict two-phase locking protocol generates conflict serializable schedules that are also recoverable, while the timestamp-ordering concurrency control protocol with Thomas Write Rule can generate view serializable schedules that may not be conflict serializable. Both protocols have their own advantages and trade-offs in terms of ensuring consistency and concurrency control in database transactions.