Exam 10: Transaction Management and Concurrency Control

A transaction is a unit of work that must be either entirely completed or aborted.

A scheduler facilitates data isolation to ensure that two transactions do not update the same data element at the same time.

Database transaction restores a database from an inconsistent state to a previously consistent state.

What are database checkpoints?

A lock allows concurrent transactions to access different rows of the same table.

The .occurs when two concurrent transactions,T1 and T2,are updating the same data element and one of the updates is lost.

Uniqueness ensures that no equal time stamp values can exist,and ensures that time stamp values always increase.

In a heavily used database management system (DBMS),the prevention and detection of constitutes an important DBMS function.

A lock locks the entire diskpage.

In the optimistic approach,during the phase,a transaction scans the database,executes the needed computations,and makes the updates to a private copy of the database values.

Atomicity indicates the permanence of the database's consistent state.

Timestamps must only have the single property of uniqueness.

An optimistic approach is based on the assumption that the majority of the database operations do not conflict.

The rule states that only one transaction at a time can own an exclusive lock on the same object.

When using an optimistic approach,during the read phase,a transaction reads the database,executes the needed computations,and makes the updates to a private copy of the database values.

requires that all operations of a transaction be completed.

The ANSI has defined standards that govern SQL database transactions.Transaction support is provided by two SQL statements: and ROLLBACK.

The information stored in the is used by the DBMS for a recovery requirement triggered by a ROLLBACK statement,a program's abnormal termination,or a system failure such as a network discrepancy or a disk crash.

Most real-world database transactions are formed by only one database request.

Incomplete or improper transactions can have a devastating effect on database integrity.