Which of the following database terms is described in the statement below? “It prevents the current
database operation from reading or writing a data item while the data item is being accessed by
another operation.”

A.
Lock

B.
Encryption

C.
Constraint

D.
Deadlock

Explanation:
Lock is the process to prevent the current database operations from reading and writing a data while
that data item is being accessed by another operation. A lock is used when multiple users need to
access a database concurrently. It prevents data from getting corrupt or invalidated, when multiple
users try to write to the database. When a lock is applied, a single user can only modify that record
to which the lock is applied. It gives the user exclusive access to the record until the lock is released.
Locking also prevents reading of unfinished (uncommitted) data.

Answer B is incorrect. Encryption provides an additional security layer, protecting the data from
unauthorized viewing with the help of an algorithm called cipher. Even if access to the database is
obtained, it will not be easy to decipher encrypted data into a readable form.
Answer D is incorrect. A deadlock is a situation wherein two or more competing actions wait for the
other to finish, and neither ever does.
Answer C is incorrect. A constraint enforces the integrity of a database. It defines the rules
regarding the values allowed in the columns of a table. A constraint is the standard mechanism for
enforcing integrity.