Exam 10: Transaction Management and Concurrency Control

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)_____.

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.

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 ROLLBACK?

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.

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

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

How does a shared/exclusive lock schema increase the lock manager's overhead?

can take place at any of the following levels: database,table,page,row,or field.

The isolation level ensures that queries return consistent results. a.Read Uncommitted b.Read Committed c.Serializable d.Repeatable Read

The reason for the different levels of isolation is to increase transaction concurrency.

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.

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

A(n)occurs when a transaction executes a query at time t1,and then it runs the same query at time t2,yielding additional rows that satisfy the query.

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

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

As long as two transactions,T1 and T2,access data,there is no conflict,and the order of execution is irrelevant to the final outcome.

As a rule,a(n)must unlock the object after its termination.

A single-user database system automatically ensures of the database,because only one transaction is executed at a time.

Time stamping demands a lot of system resources because many transactions might have to be stopped,rescheduled,and stamped.

The interleaves the execution of database operations to ensure serializability.