Exam 10: Transaction Management and Concurrency Control

A lock locks the entire table preventing access to any row by a transaction while another transaction is using the table.

ensure that a disk physical failure will not impair the DBMS's ability to recover data.

The DBMS guarantees that the semantic meaning of a transaction truly represents the real-world event.

Lock indicates the level of lock use.

The implicit beginning of a transaction is .

means that data used during the execution of a transaction cannot be used by a second transaction until the first one is completed.

The scheduler establishes the order in which the operations within concurrent transactions are executed.

The objective of control is to ensure the serializability of transactions in a multiuser database environment.

What is transaction isolation and why it is important?

If a(n)is issued before the termination of a transaction,the DBMS will restore the database only for that particular transaction,rather than for all transactions,in order to maintain the durability of the previous transactions.

The serializable isolation level is the least restrictive level defined by the ANSI SQL standard.

The multiuser DBMS must implement controls to ensure serializability and isolation of transactions,in addition to atomicity and durability,in order to guard the database's consistency and integrity.

The approach to scheduling concurrent transactions assigns a global unique stamp to each transaction.

Explain the transaction log.What is its function?

Although the DBMS is designed to recover a database to a previous consistent state when an interruption prevents the completion of a required set of transactions,the transactions themselves are defined by the end user or programmer and must be semantically correct.

A consistent database state is .