Question

Which of the following best describes the isolation property in regards to transactions?

A)Either all actions in a transaction are executed or no actions are done

B)The DBMS changes from one consistent state to another consistent state when a transaction completes successfully

C)A transaction executes with the same outcome, without any impact from other transactions executing concurrently

D)The DBMS guarantees that changes are made persistently upon successful completion of a transaction

2)Which of the following statements best describes a phantom read

A)One user reads a set of rows from a table. Another user inserts a row that matches the where condition read by the first user. The first user reads the same set of rows again getting the new row in addition to the rows that the user read the first time.

B)A select from one user calculating a summary or aggregate function (e.g. avg, max, sum, etc.) reads some rows from a table. At the same time another user is updating some of those same rows to contain different values. The first user reads some of the rows before the update changes them and reads some rows after the update changes them.

C)Two users update the same columns of the same row of the same table at the same time. One update will be overwritten by the other.

D)One user reads the same row more than once. Between the reads, an update from another user modifies the row.

3)If a schedule’s dependency graph is cyclic, then the schedule it describes is serializable.

A)True

B)False

4)By themselves, exclusive write locks and shared read locks do not guarantee serializabililty.

A)True

B)False

Answer 1

Answer:-------------

Q:- 1) Which of the following best describes the isolation property in regards to transactions?
Answer:-------
C) A transaction executes with the same outcome, without any impact from other transactions executing concurrently

Q:- 2) Which of the following statements best describes a phantom read.
Answer:----------
A)One user reads a set of rows from a table. Another user inserts a row that matches the where condition read by the first user. The first user reads the same set of rows again getting the new row in addition to the rows that the user read the first time..

Q:- 3) If a schedule’s dependency graph is cyclic, then the schedule it describes is serializable.
Answer:---------
B)False

Q:- 4) By themselves, exclusive write locks and shared read locks do not guarantee serializabililty.
Answer:---------
A)True