All data items are updated at the end of the transaction, at the end, if any data item is found inconsistent with respect to the value in, then the transaction is rolled back.Check for conflicts at the end of the transaction. No checking while the transaction is executing. Checks are ... Read More

The timestamp-ordering protocol ensures serializability among transactions in their conflicting read and write operations. This is the responsibility of the protocol system that the conflicting pair of tasks should be executed according to the timestamp values of the transactions.A conflict occurs when an older transaction tries to read/write a value ... Read More

There are three possible ways in which a transaction can be executed. These are as follows −Serial execution − In serial execution, the second transaction can begin its execution only after the first transaction has completed. This is possible on a uniprocessor system.Parallel execution − In parallel execution, two transactions ... Read More

Locking and unlocking of the database should be done in such a way that there is no inconsistency, deadlock and no starvation.2PL locking protocolEvery transaction will lock and unlock the data item in two different phases.Growing Phase − All the locks are issued in this phase. No locks are released, ... Read More

A materialized view is a view whose contents are computed and stored. Materialized view is also a logical virtual table, but in this case the result of the query is stored in the table or the disk. The performance of the materialized view is better than normal view since the ... Read More

A schedule has view-serializability if it is viewed as equivalent to a serial schedule. A schedule is view serializable if the following three rules are satisfied −Rule 1 − If Ti reads data initially, after this Tj writes the same data, in the given schedule. This sequence must be followed ... Read More

In a transaction, a data item which we want to read or write should first be locked before any read or write operation. After the operation is over, the transaction unlocks the data item so that other transactions can lock that same data item for their use.ExampleLet us see how ... Read More

Two schedules are said to be conflict equivalent if the order of any two conflicting operations are the same in both the schedules.Also, a concurrent schedule S is conflict equivalent to a serial schedule S’, if we can obtain S’ out of S by swapping the order of execution of ... Read More

Conflict serializability orders any conflicting operations in the same way as some serial execution. A pair of operations is said to conflict if they operate on the same data item and one of them is a write operation.That meansReadi(x) readj(x) - non conflict   read-read operationReadi(x) writej(x) - conflict   ... Read More

A transaction must satisfy the ACID properties of DBMS, namelyAtomicity − Execute all or none transaction.Consistency − The DB should be consistent before and after transaction execution.Isolation − Transaction must be executed in isolated form.Durability − Roll backing should always be possible in Case of any failure.A schedule is defined ... Read More