Exam 10: Transaction Management and Concurrency Control

_____ occurs when a transaction accesses data before and after one or more other transactions finish working with such data.

What are database checkpoints?

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.

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.

_____ are required to prevent another transaction form reading inconsistent data.

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

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

Lock _____ indicates the level of lock use.

Of the following events, which is defined by ANSI as being equivalent to a ROLLBACK?

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 _____ manager is responsible for assigning and policing the locks used by transactions.

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

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

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

The DBMS uses the information stored in the _____log 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.

What rule applies to the two-phase locking protocol?

Transaction is a _____ unit of work that must be either entirely completed or aborted.

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.

In the wait/die scheme, the:

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) _____.