Exam 13: Managing Transactions and Concurrency

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

The transaction recovery write-ahead-log protocol ensures that transaction logs are always written before any database data are actually updated.

____ requires that all operations of a transaction be completed.

A shared lock produces no conflict as long as all the concurrent transactions are read-write only.

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

Durability requires that all portions of the transaction must be treated as a single, logical unit of work in which all operations are applied and completed to produce a consistent database.

Explain the transaction log. What is its function?

One of the three most common data integrity and consistency problems is ____.

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

To determine the appropriate order of the operations, the scheduler bases its actions on concurrency control algorithms, such as ____________________ or time stamping methods.

What is transaction isolation and why it is important?

In a page-level lock, the DBMS will lock an entire diskpage.

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

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

All transactions must display ____.

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

Lock ____ indicates the level of lock use.

A field-level lock allows concurrent transactions to access the same row, as long as they require the use of different fields within that row.

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) ____________________.

To ensure consistency of the database, every transaction must begin with the database in an unstable state.