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.

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

____________________ control is important because the simultaneous execution of transactions over a shared database can create several data integrity and consistency problems.

A(n)____ specifically reserves access to the transaction that locked the object.

The DBMS keeps several copies of ____________________ to ensure that a disk physical failure will not impair the DBMS's ability to recover data.

____________________-level locks are less restrictive than database-level locks,but they create traffic jams when many transactions are waiting to access the same table.

A(n)____ lock exists when concurrent transactions are granted read access on the basis of a common lock.

All transactions must display ____.

A(n)____ condition occurs when two or more transactions wait for each other to unlock data.

If T1 has not unlocked data item Y,T2 cannot begin;if T2 has not unlocked data item X,T1 cannot continue.Consequently,T1 and T2 each wait for the other to unlock the required data item.Such a deadlock is also known as a(n)____________________.

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 ____________________ correct.

What is transaction isolation and why it is important?

The implicit beginning of a transaction is ____.

ANSI defines four events that signal the end of a transaction.Of the following events,which is defined by ANSI as being equivalent to a COMMIT?

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.

A diskpage,or page,is the equivalent of a ____.

The phenomenon of uncommitted data occurs when two transactions are executed concurrently and the first transaction is rolled back after the second transaction has already accessed the uncommitted data-thus violating the isolation property of transactions.

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

A consistent database is ____.

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.