Quiz
Data Concurrency and Locking
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Fragen in diesem Quiz (17)
1Which of the following describes the disadvantage of executing a set of DML statements outside a
transaction?- AThe DBMS records those operations in the audit logs since they are grouped inside a transaction.
- BThe DBMS stores the transaction operations so that the client applications can rerun the transaction
more easily. - CThe DBMS guarantees that all operations are always executed successfully.
- DThe DBMS cannot guarantee that all changes performed by the set of DML are stored, nor that in
case of an error; the changes are undone, leaving the database in a inconsistent state.
2Which of the following statements is TRUE about transactions?
- AOperations inside a transaction are executed in parallel.
- BThe DBMS stores the transaction operations so that the client applications can rerun the transaction
more easily. - C. The DBMS guarantees that all operations are always executed successfully.
- DThe DBMS cannot guarantee that all changes performed by the set of DML are stored, nor that in
case of an error; the changes are undone, leaving the database in a inconsistent state.
3To which of the following resources can a lock NOT be applied?
- ATablespaces
- BBuffer pools
- CTables
- DRows
4Which of the following isolation levels lets you see data that has been updated by other applications
before it is committed?- ACursor Stability
- BRead Stability
- CRepeatable Read
- DUncommitted Read
5Isolation levels can be specified in all of the following except:
- ASession (application)
- BConnection
- CWHERE clause
- DSQL Statement
6Application A wants to read a subset of rows from table TAB1 multiple times. Which of the following
isolation levels should Application A use to prevent other users from making modifications and
additions to table TAB1 that will affect the subset of rows read?- ARepeatable Read
- BRead Stability
- CCursor Stability
- DUncommitted Read
7Which concurrency issue is demonstrated below
Two applications, A and B, might both read the same row and calculate
new values for one of the columns based on the data that these applications reaIf A updates the row
and then B also updates the row, A's update lost.- ALost Update
- BUncommitted Read
- CNon-repeatable Read
- DPhantom Read
8Which of the following is NOT true about the Isolation Level Currently Committed?
- AReader does NOT block Reader
- BReader does NOT block Writer
- CWriter does NOT block Reader
- DWriter does NOT block Writer
9The following scenario describes which concurrency issue?
1) Application A updates a value
2) Application B reads that value before it is committed
3) A backs out of that update
4) Calculations performed by B are based on the uncommitted data- ALost Update
- BDirty Read
- CNon-repeatable Read
- DPhantom Read
10Which of the following commands are NOT classified under Transaction Control Languages?
- AGRANT
- BCOMMIT
- CROLLBACK
- DSAVEPOINT
11Two applications have created a deadlock cycle in the locking subsystem. If lock timeout is set to
30 and both applications were started at the same time, what action will the deadlock detector take
when it "wakes up" and discovers the deadlock?- AIt will randomly pick an application and rollback its current transaction
- BIt will rollback the current transactions of both applications
- CIt will wait 30 seconds, then rollback the current transactions of both applications if the deadlock has
not been resolved - DIt will go back to sleep for 30 seconds, then if the deadlock still exists, it will randomly pick an
application and rollback its current transaction
12Which of the following is true about isolation levels?
- ARepeatable Read is the default isolation level
- BRead Stability is more strict than Repeatable Read
- CCursor Stability has no dirty reads
- DUncommitted Read has no non-repeatable reads
13Application A is running under the Repeatable Read isolation level and holds an Update lock on
table TAB1. Application B wants to query table TAB1 and cannot wait for Application A to release its
lock. Which isolation level should Application B run under to achieve this objective?- ARepeatable Read
- BRead Stability
- CCursor Stability
- DUncommitted Read
14Which of the following is NOT true about transaction?
- AA transaction provides atomicity
- BAfter a transaction to the database is made it can be made permanent (using the COMMIT
command) - CInitiation and termination of a transaction defines the point of data consistency of data with the
database - DCOMMIT statement is NOT needed in a manual-commit
15How many transactions are there in the following SQL statements?
CONNECT TO DB employees
INSERT INTO employee VALUES (100, 'JOHN')
INSERT INTO employee VALUES (200, 'MANDY')
COMMIT
UPDATE employee SET empID=201 where name='MANDY'
COMMIT
DELETE FROM employee WHERE name='MANDY'
UPDATE employee SET empID=101 where name='JOHN'
ROLLBACK- A1
- B2
- C3
- D4
16Which of the following is TRUE about committed data?
- Adata is consistent with the database
- Bchanges cannot be committed manually
- Cchanges cannot be committed automatically
- Dchanges can be reversed with the COMMIT command
17Assuming the employee table in the employees database is initially empty. How many rows will be
in the employee table after executing the following commands:
CONNECT TO DB employees
INSERT INTO employee VALUES (100, 'JOHN')
INSERT INTO employee VALUES (200, 'MANDY')
COMMIT
DELETE FROM employee WHERE name='MANDY'
UPDATE employee SET empID=101 where name='JOHN'
ROLLBACK- A0
- B1
- C2
- D3
Informationen
- Beschreibung
- Quiz am Data Concurrency and Locking, erstellt von 2014068975 am 08/10/2015.
- Autor
- 2014068975
- Sprache
- English
- Aufrufe
- 2
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