Database Transactions and Security
An operation that a user performs against a database that retrieves or alters the data in the database should adhere to which of the following properties?
ACID
Within the scope of database security, to what does availability refer?
An enterprise must have access to its data at all times.
What is a database transaction?
An operation conducted by a single user against a database that retrieves or alters the data in the database
Which of the following database transaction properties states that a transaction is a complete unit that executes in its entirety or not at all?
Atomicity
There are several countermeasures that an enterprise might use to secure the data in a database. Which of the following countermeasures would require a user to enter a user ID and password to access database data or use authentication to prove their identity?
Authorization
What is the term for the final step in the successful completion of a database transaction in which the database attains a new consistent state?
Commit
What is the term for the process of managing simultaneous transactions so that they do not conflict with one another?
Concurrency control
Within the scope of database security, which of the following refers to the need of an enterprise to maintain control over sensitive data?
Confidentiality
With regard to databases, to what do the properties of atomicity, consistency, isolation and durability refer?
Database transactions
What is the term for a situation in which two or more transactions are simultaneously waiting for another transaction to release a lock on a data item?
Deadlock
Which of the following statements about using the timestamp method for concurrency control is true?
Each data item is assigned a read timestamp and a write timestamp.
How can you reverse the effects of a committed transaction?
Execute another transaction that reverses the changes made by the first transaction.
When should optimistic concurrency methods be used for concurrency control?
In situations in which rollbacks due to conflicts are very rare
Within the scope of database security, to what does privacy refer?
Information about individuals must be kept confidential.
Within the scope of database security, which of the following refers to the fact that data that is not kept secure cannot be guaranteed to be accurate?
Integrity
There are several countermeasures that an enterprise might use to secure the data in a database. Which of the following countermeasures prevents invalid data from being entered into the database?
Integrity controls
Which of the following database transaction properties states that each transaction is independent from other transactions?
Isolation
What does the locking method of concurrency control do?
It prevents a concurrent transaction from modifying or reading a data item while another transaction is accessing that data item.
Concurrency control can be viewed as a means of achieving serializability. What are the two methods that allow transactions to execute concurrently and safely?
Locking and timestamp
Concurrency control is designed to address several problems, one of which occurs when one database update overrides another to yield incorrect data. What is this known as?
Lost update
A transaction has a write lock on a data item. Which of the following statements is true?
No other transaction can read or write to that data item.
Which of the following statements about a committed transaction is true?
Once a transaction has been committed, it cannot be rolled back.
Which type of concurrency control should you use if data access conflicts occur very rarely?
Optimistic concurrency control
What is the term for the process used by a DBMS to determine whether a set of transactions will produce the same result as some sequential (non-overlapping) execution of the same transactions?
Serializability
What process does the DBMS use to find nonserial schedules that allow transactions to execute at the same time without conflict?
Serializability
With regard to databases, to what do the concepts of confidentiality, privacy, integrity and availability refer?
The scope of database security measures
How do timestamps prevent database transaction conflicts?
They roll back any transactions involved in a conflict and restart them.
What is the term for a unique identifier assigned by a DBMS to a transaction in order to prevent deadlocks?
Timestamp
Which of the following is a popular method DBMSs use to detect and prevent deadlocks?
Timestamps
For what are the SQL keywords BEGIN TRANSACATION, COMMIT and ROLLBACK used?
To delimit a transaction
Why are concurrency control and database security important?
To ensure that a database is stable and remains in a consistent state
What is the term for an operation, or series of operations, conducted by a single user against a database that retrieves or alters the data in the database?
Transaction
Concurrency control is designed to address several problems, one of which occurs when a database query accesses only partially updated data. What is this known as?
Unrepeatable query result
There are several countermeasures that an enterprise might use to secure the data in a database. Which of the following countermeasures would be an effective way to hide many parts of the database from unauthorized users?
Views
An operation that a user performs against a database that retrieves or alters the data in the database should adhere to a set of properties. The durability property states that:
a committed transaction is permanent and should not be lost owing to any ensuing malfunction.
An operation that a user performs against a database that retrieves or alters the data in the database should adhere to a set of properties. The consistency property states that:
a transaction must change the database from one stable state to another stable state.
A database transaction can have either of two results: one that successfully changes the database data and one that does not. These two results are respectively known as:
commit and rollback.
There are several countermeasures that an enterprise might use to secure the data in a database. You would use backups to:
create copies of database data and the log file to ensure data access and security.
There are several countermeasures that an enterprise might use to secure the data in a database. You would use encryption to:
encode database data, particularly sensitive data.
Concurrency control is designed to address several problems. An uncommitted update problem can occur when:
one transaction is allowed to see the intermediate results of another transaction before the first transaction is committed.
Timestamps provide an approach to realizing serializability. You can use timestamps to:
order all transactions so that the oldest transaction receives priority in case of a data access conflict.
The two main types of locks you can use to apply concurrency control to database transactions are:
read locks and write locks.
The final step in a database transaction is a commit, which means that:
the transaction completed successfully and the database has attained a new consistent state.
A database transaction has experienced a rollback, which means that:
the transaction failed and the database has been placed back into the consistent state it was in before the transaction.
Deadlock occurs when:
two transactions are waiting for access to a data item that is locked by another transaction.
